Tell me more about the ToEE engine.
I tried to play that game some time ago, but just couldn't get into it. I remember it had great turnbased combat, and was a rather faithful recreation of D&D rules.
Did ToEE's engine have any notable flaws?
It has a very nice rules-implementation and the best combat-engine in an rpg to date, but the engine overall is pretty crummy.
Flaws?
-2D engine (so the camera is really constrained)
-Hand-drawn maps (makes it hard to make your own maps)
-Really scuzzy performance at the time it was released
-All friendly creatures can freely interpenetrate
-Jarring juxtaposition of really detailed jpeg maps and really low-poly 3D models
-Not many models (hard to create that many different monsters)
I'd cast my vote for the NWN2 engine. Performance isn't wonderful, but it's fine (if you don't go nuts with the shadow options), the only crashes are easily avoidable (they claim to have fixed the last of them in the latest patch), the RTwP combat engine isn't as good as ToEE's (doesn't have all the 5' step and reach games), but it does a lot (wide spell selection, disarming, lots of little special abilities) and it looks ok doing it.
Most importantly, with the toolset, it's fairly easy to make anything you like. The game doesn't ship with all the art you might want, but making custom building models, re-texturing stuff and the like is pretty simple (to judge from the amount of it) and it ships with all the terrain art most people would want. The only real deficiency is in character models, but there are still plenty, some user-made ones available and more on the way.