With 12 Disciplines, each with at least 6 Deeds to pick from (bare minimum 4 "basic" and two "advanced"), you're talking a bare minimum of 12 pages, and those would be small Deeds IMO, six to a page is squeezing tight. That would technically fall short of your goal (9+12=21, not 25), but I feel reasonably confident that this would meet the need.
As for the fiddly nature, even just having skill points at all is pretty fiddly already. 6e, at least IMO, has a very low but nonzero chance of having more fine-grained skills than 5e or 4e did, but it's not going to be all the way back to 3e/PF1e skill points. More like degrees of scaling. 4e had three states (untrained +0/some actions locked, trained +5/all uses unlocked, focused +8/no further unlocks), and 5e has about three and a half (non-proficiency, the rare "half" proficiency, proficiency, expertise). I could see codifying a fourth stage, call it Mastery, which only some classes get. But that's neither here nor there.