UFO is a case where I will defend the system's design to the core, but cannot say the same for how it was implemented and worked out in-game.
Really though, I couldn't really answer what mechanics I would like to see. I will say that I would like to keep the intention of a simpler, less tricky system. Not gimmickless, nor necessarily simple under the hood, but simple to play. I think DDC was a step in the right direction, but the execution of DDC's design was uh unfortunate.
I would be fine with or without the Power system. I don't think it's really necessary anymore, but I don't mind its existence.
I would definitely like to avoid a graze-heavy system, though. After IN, SA and UFO, I've thought way too much about how to design a graze system that isn't inherently dependent on supergrazing and/or heavy milking, and the solutions there are are pretty complex. I have trouble believing that ZUN making a scoring system with graze as a core factor would ever not devolve into supergrazing or tons of milking.
(a maximum of six misses in a run without trance is just ridiculous)
Play some other STGs and then come back and see how silly this sounds lol
I actually liked IN's way of handling deathbombs
What about them, that they lasted for far too long and wasted two bombs if you didn't bomb on the first frame?
I'd like to see less "literal" spellcards, if that makes sense.
I agree with this general sentiment. I think it's gotten really obvious since TD, but it seems as though ZUN is trying a bit too hard to make many patterns fit a special intention rather than just being thematic, and I think it really interferes with his pattern design.