What I would love is a system which reworks all 5e monsters to: (1) fit in a one-line stat block with extra information for special actions; (2) have the same save for everything, and for that save to be based on HD/CR; (3) have their CR based on their HD or vice versa; (4) have a tag-based system where adding the 'fast' or 'spined' tag adds +5 to attack or +2 to damage or whatever; (5) have simplified damage maybe? 5e is such a punchy game that you end up throwing huge quantities of dice for attacks, so that may be unfeasible.
@Sandra I saw your other post while looking around, but I missed this excellent one! I very much enjoy what I've seen of your blog/wiki (bliki) so far.
https://idiomdrottning.org/one-digit-monster-stats