Is there an option to respec?

I've made some poor decisions (in hindsight) leveling up some of my characters. Are there opportunities later in the game to rectify the situation by redoing skill points, feats, etc.? If so to what degree, would it be possible to change character levels?

It was finally added in base game, same NPC that lets to recruit mercenaries. But it is limited by difficult setting

There is no "official" way to respec, and I haven't seen anything in the forums saying that the devs are planning to add it.

There is a 3rd-party tool which allows you to modify your saved game to reset characters to their starting level (0 for your main PC, the level they join at for the NPCs).

Whether or not it does it 100% perfectly (some people have reported not getting the bonus feat or bonus skill point for humans... may have been fixed now), or if it can cause bugs with the game down the line is unknown. Use at your own risk.