Regarding the keep I would tweak a few things (in addition to
Mastermind 's suggestions), then hopefully major changes will come.
1) Make the upgraded keep the best place to rest, not the shittest place.
2) Don't let structures get destroyed with auto-defend, that's just annoying and can lead to weird bugs if the upgraded keep is destroyed.
3) Better merchants, the current system has shitty random drops for some rare items, so you'll never come cross some great gear if the RNG Gods will it, some of this gear should become available or commissionable once the keeps shops are up and running.
4) More people need to give a shit you're the lord of Caed Nua, you should have political enemies, there should be a few short flavour decisions like with the BG2 keep.
5) Areas around the keep need to be expanded, fields, perhaps a small town, some areas where you could make a bit of narrative around the keep and have a few battles.
6) Just a few touches to expand existing systems, like having the option to execute prisoners, a nice cosmetic touch would be a further option to put their heads on pikes or nail them to the keeps walls etc, lowering prestige but raising the security of the keep with the intimidation factor. You could even interact with the souls being a watcher.
7) You should get some tangible reward for completely upgrading the keep.