There's no way to really do this how you're describing. You can't effectively move ragdolls around with "applyforce" like you are saying.
The only way to get models moving in any kind of efficient manner and ESPECIALLY to make them look lifelike, you HAVE to have the animations built into the model. I'm sure you could create some kind of stupidly complicated system to move the bones in sequence, but that would be a hell of a lot of work, for a very sketchy output.
Also, you don't "weld" or "ballsocket" different parts of the same model together. You CAN weld a ragdoll to itself to lock bones in place, but you shouldn't be using too many constraints on just one entity, they're meant to be used between entities (or an entity and the world)
tl;dr - your approach is impractical and you should NOT every code any kind of SENT/SNPC like this. Use base models with the animations built in, and code them with the built in SNPC API (I know it sucks, but it's what we have right now)
Making ragdolls move have been done in wiremod e2's before and they've looked pretty good in some cases too. If someone is dedicated they should be able to make it look and work nice.
Honestly this could be done with wiremod only so I don't see why you think it's impossible or too hard to do. Maybe it's not worth the money or whatever but it's still possible.
Converting an e2 to lua shouldn't be to hard if you are willing to call yourself good at lua. I mean all the logic and structure is basically the same.