Glad to see you found the forums, MrJane! Tommy from your steam post here

I recall someone from Larian replying to a topic regarding making new calls for hp value absolutes etc. He implied it could potentially be possible to add at some point if my memory serves. So if that's achieved at some point, it isn't too far of a stretch to get a health bar system working, I'd imagine. But it comes down to resources > demand too I guess. If the absolutes calls are added to the modding tools at some point, and also opening the doors for UI modding, then I'd say it's very much achievable. But until that day... ^^
I think it sounds like a neat addition to the game too. If not as an optional setting.