Heya! Good answers earlier by you!
Yeah I think I'll have to get into that, but I'm starting to run into the limit of not being a programmer myself, and information is pretty scarce on ATproto. The article differs from their own federation architecture description from earlier in the year, simply because its outdated and noone has formally written down the new info, so that was a bit of a struggle haha https://blueskyweb.xyz/blog/5-5-2023-federation-architecture
At any rate, the PDS's are amenable for sure. Robin Berjon is the furthest along with thinking here, with his AP over AT piece: https://berjon.com/ap-at/ Responses I've seen havent suggested its technically impossible, but probably difficult for reasons that I tuned out of reading because I didnt understand :D
Beyond that, people keep talking about the lexicon and how that at is core is also versatile; similar to how fedi has Mastodon's type=Note that everyone uses, even though you can create any 'type' you want. I'm pretty sure that nobody has done that yet tho.
Oh thats an interesting question! I'm assuming you are talking about the UX/UI of instance selection?
And thats not something I have written about (neither does another article pop into my mind either sadly), but interesting idea for an article for sure to write about