If you signup to social media it will pester you for your email contacts, location and hobbies/interests.

Building a signup wizard to use that information to select a instance would seemto be the best approach.

The contacts would let you know what instance most of your friends are located (e.g. look up email addresses).

Topic specific instance, can provide a hobby/interests selection section.

Lastly the location would let you choose a country specific general instance.

It would help push decentralisation but instead of providing choice your asking questions the user is used to being asked.

Wikipedia lists all 12 subs as having Rolls Royce Pressured Water Reactors.

Your PWR reuse idea is is kind of where Rolls Royce is looking to go with Small Modular Reactors (https://www.rolls-royce.com/innovation/small-modular-reactors.aspx).

I suspect refurbishing decades old PWR reactors would be far more expensive than just building new ones, for example a SpaceX Merlin engine costs $1 million and a Blue Origin BE-4 costs $15 million. Nasa argued it would be ‘cheaper’ to reuse Shuttle components for the Space Launch System (SLS). Refurbishing Shuttle RS-25 engines has cost Nasa $50 million dollars per engine, restarting a production line is costing $100 million for each new RS-25 engine.

Tesla actually market it as a positive.

Car manufacturers have to setup different manufacturing lines to provide different feature levels. Tesla argue this makes them more expensive. Tesla cars have all features installed, just disabled and the optional extra packages are cheaper compared to their rivals as a result.

To be honest there is a certain logic, if you’ve ever been in a Ford Focus LX (bottom range) its pretty clear they had to spend quite a bit of money on more basic systems. I honestly thought each LX was sold at a loss

You’ve just moved the packaging problem from distributions to app developers.

The reason you have issues is historically app developers weren’t interested in packaging their application so distributions would figure it out.

If app developers want to package deb, rpm, etc… packages it would also solve the problem.