Basics
Start with 5e, but re-do the numbers. Something like 5e advanced. Specifics to come.
Numbers
5e's problem is that the part of the numbers you can jigger with (proficiency, mostly) is too small, so the focus has shifted to ability scores. This has led to a mad rush on ability scores that has just kind of broken them.
Proposal: let's get bigger proficiency bonuses. How big? Well, 1/level seems big enough...except at 1st level, it isn't quite. How about 3+1/level? Sounds arbitrary? Well, that's the skill point cap.
Ability Scores
Ability scores: 20 point buy unweighted, as in 6d20. +2 points every 4 levels, or possibly a tier bonus.
You can get racial bonuses, but not huge ones, and only with your starter levels. MAYYYYYYbe you can get a few small bonuses from monster paths, but I don't want people chasing ability scores for numbers. I'd rather have a Dragon who occasionally becomes a full-size dragon with a 45 strength than one with a constant +8 Str. Same with vamps. Temporary huge buffs with costs are better than constant small buffs.
Also: monster buffs should overlap magical ones. Hahaha suck it.
Progression
Skills have their own thing now, although they could perhaps be all-or-nothing (spend 1 "skill", suddenly get 3+1/level ranks). Who knows.
Other things to gain as you level:
- Feats
- Stat Adds
- Paths
One possibility:
- 1st: feat
- 2nd: path
- 3rd: feat
- 4th: stat add
- repeat
Skills
Just port 'em from d20.
Feats
See /5e/Feats
How many? More than every 4 levels, maybe not 1/level.
Secondary Power
How to get a vampire to the right power level? Paths.
Also, PCs shouldn't necessarily be at monstrous power levels.
Paths are like 5e, but not class specific (although they can be, there should be plenty of non-class-specific options).