If appropriate it would be interesting to hear what sort of project you are working on.
Very few customers modify their robots, as it is sort of a hobby among skilled craftsmen, electronic engineers and technicians, often retired. This is not a general consumer website, more a technician and hobbyist site (though as a result we have the most information...).
Atop the Neato forum here you will see an index thread i maintain which tries to catalog all the modifications threads on the Neato, many which I did myself, usually with no followers.
Modifications were originally due to very poor, cheap construction of the robots, and absence of useful features slowly added to new models over a decade (they started in 2000 with Roomba). So member Vic7767 here had a business selling ball bearings to improve construction of Roomba's flimsy product prone to failures.
One mod of interest was due to earlier models using rapidly worn out NiMh batteries instead of lithium batteries only common last couple years; these bots make heavy duty battery use compared to other devices, more like an electric bike, or a power tool, and needing almost annual replacements. So early mods included ways to assemble your own longer life lithium battery and finesse the electronics for charging it involved, still used by some on old Neato and Roomba bots. One company began selling replacement lithium batteries for the old bots with included adapter electronics, and then all the new model bots came with lithium. Vorwerk was the first with its earliest Neato upscale version. Lithium became practical with advances in the chemistry making them safer than the kind in laptops and phones, for their large size more like car batteries, with power tools going to it a few years ago. LiNMC chemistry.
Early robots did not have WiFi communication and a number of electronics hobbyists and engineers worked on adding components to Neato robots for this purpose, one of which is now a permanent thread atop this forum. Lots of old models still in use. Engineering students can also have an interest in such projects. Now with all the WiFi equipped models, programmers, hackers are attracted to fiddling with the app software (Xiaomi originally had not English language and all sorts of hacks were provided by software expert users). The Alexa integration now popular is supported by Amazon
for programmers, DIY, so there is a potential for a lot of hacking there not yet seen.
Two Neato mods have been used by several users. First is adding a slider plate underneath to improve movement on some carpets on which the robot could not move (robots have never been able to move on deep pile carpet or shag carpet much; some carpets are also slippery). Today you see the recent Xiaomi Neato competitor has a floating intake design preventing it moving on lots of carpet even regular Neato's navigate. But I like the big Samsung robot with larger wheels which handles carpets better without modification.
The second Neato mod, and for other brands, used by others has been adding a strip to the bumper to lower the bottom edge, so the robot does not climb onto low things on which they get stuck like a cat in a tree. Especially cantilever and tubular leg chairs, like from Ikea. Finally a German enterprise started selling a ready made self-stick strip for Neato's and Roomba's. The designers seem oblivious to this need.
The early Neato's lacked a side brush so I added one, but only a couple other people have tried it. They were added to the Botvac
second generation several years ago. This allowed discover such side brushes are useless on carpet, and have other problems. Popular for hard floors though, customers want their corners cleaned. Samsung has made a different solution in their new 7000 series, with a suction direction shutter on the front.
Design defects continue even in the Samsung I use. I have widely publicized a software defect which causes the Powerbot to shut down in certain contacts with furniture legs, easily worked around by disabling a sensor detecting when the wheels are extended as when the robot climbs, in the suspension (just tape it in or whatever, "Side Bumper Extension and Tilt Reduction Mod" Samsung forum. There is also a tilt reduction mod for Neato's. Another Samsung defect is insufficient bumper length along the side, allowing mine to climb onto floor lamp bases and get stuck. The Guild of Modifiers to the rescue. No takers anywhere else have reported though. Improved in the newer 7000 series started this year. The way the companies work, I will be surprised if Samsung ever fixes the software error, though I finally got it forwarded to headquarters via their own forum -- if it goes anywhere in that huge company bureaucracy. They put their resources into new dubious things like smartphone apps they think will attract customers -- whoever has the fanciest app wins...
This is why there is interest in the work of member third_deg here, former Roomba designer starting his own company, Third Degree, if it ever happens; maybe he will get it right for a change. Slow process filing patents.
Another Neato mod only a few have used is for the robot getting stuck by pressing itself underneath a sofa or something, an over head pinch trap. Someone market actaully a little stick on thing for Roomba's with the same problem to prevent this, and I showed how to easily add a wire loop to the Neato bumper to prevent this. Then Vorwerk added an overhead sensor onto the laser turret like they should have -- and Neato's models still lack it. The camera guided bots are less affected because of better optical sensors. An old expensive Karcher self-empty robot had top sensors for it. Some of these problems are addressed by raising the problem furniture a little with wooden fittings etc. instead of fixing the robot.
Now your second question about customer relations and what not, I am not sure entirely what you mean. First notice that most of these robots, lacking washable filters like Samsung, Dyson and some, require buying regular supplies to make them work -- not to mention previously, annual expensive battery packs. So there is an issue with whether a company can be counted upon to supply these things for several years use of an expensive appliance.
Beyond these "consumables" though is an issue of spare parts to repair broken machines, electronic circuit boards and what not. Samsung does a full scale appliance standard parts supply. I am not sure about Roomba, but Neato Robotics supplies parts only to warranty service contractors, good only for year. Lots of old Neato parts get sold on ebay
, used, but not for newer models. Of course, technical skills are needed to make repairs. Yet there are small businesses (member Medtech here in Russia repairs, as does Vic7767, and Shirgal in Israel) -- where do they get parts?
There are often questions about technical issues with the robots, being both complex and limited in use various ways not disclosed, with carpets and so on, and some makers, like Samsung, have customer advice forums on their websites. Get the community to respond besides bothering customer service reps, common throughout the electronic tech industry now.
What about warranty repairs? Neato and Vorwerk are reported slipping badly with dubious outside contractors.
What if it is out of warranty (post your problem here...)?
For example, a question raised a few times was how can you schedule the robot to make two cleaning passes through the house instead of the one supported in the software -- if customers even realize that limitation. A trick was found for this on Neato's.
Lots of questions here are "this or that doesn't work right, what can I do?" as if they did not bother to ask customer service. Well, customer service reps are not supported well by the engineers, and often know nothing more than the user guide info. A common problem in the whole very complex tech device industry, and squarely management's fault, not the tech rep's.
I use a prepaid Tracfone cell phone because not calling a lot so cheaper, and if you look at their site they have all sorts of tutorials on usage of the different smart phones, which are very complicated -- virtually PC's... I don't see that at vacuum robot makers.
Of course, if they made better robots with fewer limitations on use their would be fewer questions. The companies don't want to advertise their limitations, it is difficult to do so without denegrating the product. The software industry has long had a different attitude, with the frequent updates to fix identified problems etc. -- all due to business, commercial use with maintenance operations, the complexity of those systems etc.
It has always been a matter of cost -- a good job could be done with a $10,000 industrial class robot, but the issue is what can be done at a consumer device price? Not everything it turns out, leading to all sorts of things like this website.