Well, here would be some of my changes:
1. remove "jank"-KOs
- upB -> hitboxes less disjointed
- sideB -> hitboxes less disjointed/smaller
- dtilt -> ~2 frames more endinglag
- "3rd jump" removed
- witchtime -> a pre-programmed counter attack similar to Lucario or something, where the opponent is slowed down while Bayo does like 2-3 hits or something (at first I thought about reducing the slowdown-time to about 66 %, but the main problem is still there... upBs or dsmashes could still easily set up for kills at any %, making it too risky trying to attack her, which is just too stupid imo)
- upB
-> multihits now connect properly (can't fall out above to die off the top)
-> vertical distance the move travels shortened a little bit (making it harder to drag opponent out at the top)
-> less BKB (even if you don't fall out it's still too strong for a frame 4 move that combos off grab/uairs and can be done OOS)
- downB
-> less intangibility frames (startup 3->5?, and stop earlier as well)
-> downB kick hitbox a bit smaller, KB also lowered a bit
- downB -> a few frames more lag at the end
- Luma
-> longer time gone when KO'd (15-20 seconds maybe?)
-> attacks (especially uair) have less BKB (to not be able to KO at the top/side at like 0 lol)
- uair to upB strings weakened (uair a little more endinglag and/or higher KBG)
- no more ding dong kills at early %s (still usable for combos at lower %; aka add more(?) KBG on cargo utoss)
+ make this char better in other ways, like: dsmash more KB (upper hitbox back from Brawl), fair a little less endinglag/make autocancel work, much less upB landing lag for a "good"/"lagless" landing, downB less endinglag in the air and less landinglag from it (to be able to use it to reverse momentum more and make it a little easier for this character to land, which is his main weakness)
- no more early koo-pa kills (maybe still combos at lower %s)
+ add some invincibility on grounded upB again (like in Brawl?)
- upB -> no screw attack first hit jank kills
- upB -> no parasol jank kills
2. weaken some options which are too strong
- dtilt -> more KBG (so it can still combo at low %, but won't combo into KOs anymore)
- sideB -> grab hitbox of sideB ends a little bit sooner (1-2 frames less active at the end?)
- reduce weight by like 1-3 points (it feels like he lives just a tiny bit too long)
- fair -> autocancel window reduced a little bit (harder/impossible to string fairs)
+ fair -> a little more KB again
+ dash attack -> less endinglag, to make it more like Brawl. I'm biased for this move because it was amazing and is now much more useless, make sure it won't combo into any kill confirms, though
- uair -> a little less lingering hitbox (hitbox disappears sooner), also like the 1 frame more startup suggestion
- limit -> no charge from getting hit, no or much less "stat-buffs" while having full limit
- limit sideB -> less invincible frames (10-> 5? or something), a bit less knockback
- limit downB -> lower KB (somehow making it able to not be completely broken in doubles), but now does more %
- nair -> hitbox a little smaller
- uair -> does ~2 % less
- dair -> remove landing hit (or give it less hitstun to not set up into free usmash-KOs)
- somehow make fair->footstool not work anymore (harder to fall out of middle hits?)
- dashgrab -> a little more endinglag (~2 frames?)
- neutralB -> a little more endinglag
- downB -> a little less KB for wafts so they won't KO at ~30 with rage
+ old (Brawl) fsmash back..
3. fix "broken" stuff (broken as in too good or unintended difficulty; aka fix Luigis downB)
- downB -> cyclone middle-hits now have a little less hitstun, so it can still be used to gimp, but not as well/crazy
+ downB -> easier to mash (you can now buffer the inputs to make it more bearable to play this char [still not easy to mash perfectly, but possible for a normal human being..])
+ just a tiiny bit more air mobility/deceleration to help him trying to land/get out of juggles :]