The dev time required for that likely just isn't available. People aren't not buying Blitz over this either.A few changes:
1) That (Flame Notes are 100% useless now)
2) Double or triple Runaway Notes points - Runaway Notes are useless now, they'd be somewhat interesting at 30,000 points
3) Boost Shockwave just a bit (again, not useful for most styles of play, a slight bump could actually make it viable in a Pinball build over Bandmate)
4) Maybe boost the instrument powerups slightly (Synch is too good too often right now, slight instrument boost would help most non-pinball scores).
It wouldn't be perfect, but it'd offer all kinds of options for GSing songs, and a few options for leaderboard chasing, and most of the tweaks I'm suggesting wouldn't change the average player scores that much.
I mean, of the untouched powerups, Road Rage is fine and has it's place, Bandmate is fine as well (it complements the top tier playstyles, but it's not the cause of any issues by far), Blast is fine, Point Doubler is safe, and Jackpot is generally well balanced risk/reward style of play.
Edit: If they were to patch, dropping the timing window slightly and/or prevening the hitting of 2 adjacent note, and increasing the value of notes themselves and Blitz Mode would probably fix things even better. They'd probably also be best in refiguring the star formula a bit at that point if they want to keep the star chase about where it is.
It's not that I disagree with your suggestions...I'd be inclined to agree with all of this if I were in charge of the game. I just think that given the fact that they're largely moving on from the game here, it seems like the easiest thing they could do is just send it back to the way it was.