I know pretty much nothing about topre, but I am quite sure that the main reason people don't do that is simply because it's hard to source the switches compared to mx and it's also hard to work with the capacitive aspect of the switch, so I assume that most people prefer doing customs with mx since there is already enough challenge in general that these 2 factors discourage people.
Also, some people make custom boards for themselves, but many create a project to be shared with the community and produced in some quantity. If the only way to get switches is to salvage some from rare boards, it makes it near impossible to then organize a GB for this custom.
But if you want to do it for yourself, go ahead, it's 100% sure you can do it. Probably a lot of work as always, but it's doable I am sure.