I thought about Svelte + Tauri. Desktop but with Web flexibility. It also allows adding other fediverse as plugins.

Yeah, and this post about how to use some (a lot of) servers that are doing nothing to participate in "pros" while the top 20 of servers are suffering from these cons.

Huh, so the problem is about just serving static assets? TBH, I think this problem should be mostly solved, especially for such minimalistic UI. Maybe some (free) CDN? Also UI can use any lemmy server for most of requests (e.g. fetched federated_servers fom a bootstrap node) and use "logged one" only for user actions. I think it isn't a terrible difficult task for the current ui (it has it's own backend).

As I said, there is no profit from empty instances. Of course, the federation itself is good and fail-proof in this way. But if nobody asks for this cache, it's just an Internet Archive of a sort.