There is still people who love the old one's because of the excellent keyboard and the tough shell while the new models have bad keyboards and a really fragile shell (it just does not feel sturdy anymore).
Maybe the market is not big but I said it is there and not how far you will be able to scale that. Probably enough for a bunch of people to become millionaires.
I switched away from TP after my last model from 2006 was not modern enough for my taste anymore and I didn't have the time to upgrade it myself. Without USB3 and limited because of the CPU it is not an option for me anymore and I would have loved to let a company upgrade it so I can use it 10+ years to come.
And there is still an x200 that I will keep for some x-mas tinkering time to try the libreboot-mod myself.
After all I would be very glad if I could find an x201s some day and mod it / let it be modded by a company so it is not only usable to do some retro stuff but actually useful in the modern times.
The logistics will only get cheaper, faster and more secure and I would not see it as a problem. At the moment we see AMZN pushing into the market while China builds it's "Belt and Road" project. All of these developments will have a positive effect on logistics for consumers and vendors probably.
The hardware for mods may be cheap but you have to add the working hours you need to achieve a mod. Of course it may be reduced by experience.
I often think about doing things like: Is it worth the (cheap) money AND my time?
Sometimes I do it though it is (more) expensive because I also learn a lot but other times I am in a hurry and already stressed enough and would prefer to outsource this kind of work. Especially in the field of customizing (electronics) there is a lot of market share for (small?) companies to be earned.