Thanks a ton for this detailed response!!
I think thats a really good shout to lower the initial difficulty - watching others play its clear night 2/3 was too soon to throw that many that fast, without having a solid grasp of the controls
More upgrades and randomness I absolutely agree, it'd add a lot of variance and more suprise to the shop phase. Changing up the mechanics per colour could be good too, it means you'd have to adapt stategically.
I think you nailed some good ideas, thanks once again!