IMHO rather than jump into the jungle of “this block plugin offers 100 structures…” - e.g. accordions, FAQ’s, etc. I would like to see the existing blocks refined to allow for greater flexibility.
My top element would be to introduce the concept of “GRID” CSS alongside Flexbox. Also enhance the Flexbox options so that they mimicked what is available within that system. GRID (IMHO) offers great flexibility in those areas of fixed formats where Flexbox is great a responsive flow. Of course both overlap.
BOTH would be a great combination and beat just about everything out there on the market.
I would still prefer you to maintain your “you do the design - we provide the tools” approach. As soon as you jump on the tie-in between theme and block plugin you join ALL the other “page builders” and annoy a lot of us developers who like GB and GP for the flexibility they offer us.