There is nothing like this availlable currently. Framework probably comes closest, but they only sell in a few countries, and there is lots of stuff to dislike about their solutions - but building your own around a framework board might be feasible.
I have two mnt reforms - as you said, slow and expensive. They have their use for work prototyping for me, but generally wouldn't recommend. They also have the worst keyboard I've encountered in a notebook in the last decade.
I nowadays manage my private stuff with the ansible scripts I develop for work - so mostly my own stuff is a development environment for work, and therefore doesn't need to be done on private time.