I agree with a lot of what you are saying. I also really enjoyed 1-50 base game of early Swtor and feel like Bioware is just making this into a expensive singelplayer game with the newest expansions.
I would like that Flashpoints became level based again ex Athiss lvl 21-25 and that rolls like tank and healer matters again. Not so much fun being lvl 25 tank when you got 3 lvl 65s in your group just smashing their way trough everything and at every boss you have healing nodes you can just touch so no one feels like a healer is required anymore. No to me Flashpoints were more fun in the old days.
I would also like new Races (Nautolan!) more fun side games such as Pazzak and Swoop races, more fun PVE and PVP content and that they make gear throughout the entire playtrough matter again (Also random drops on planets and hard enemies would be cool) Some new leveling zones on existeing planets such as Korriban or Tython would be really fun and lets us go back to the planets we already like.