The bolded bit, below is the only maybe slightly helpful comment, if you want to just skip to it...
They say sometimes the point is the journey, not the destination, and you're sure sign'n up for a long one....
Seriously, though, I suppose you could approach the 5e SRD like the d20 one and come up with something, but 5e really did put a lot of effort into being evocative of the classic game - prime grazing land for sacred cows & such - it almost seems a shame to try to make it into a classless system. (OK, when I said, 'Seriously,' I obviously misspoke...)
It'll likely work better if you don't get stuck trying to reverse-engineer the existing classes. That is, don't get hung up on it if you find that re-building the existing classes results in them having very different point values. That's just D&D be'n D&D.
Can't argue with that.