Yes, grounders are the very reason why I started working on this in the first place. My dog model has 3 bones in each leg, so it was no longer a trivial trigonometric problem.
I'm thinking there are two possibilities to implement feet lifting off.
1) Be able to specify a weight from [0..1] on each effector to control how much influence the solved chain will have. This will allow you to specify 0 when the foot should lift off and 1 when the foot touches (and you'll also be able to blend between, which I think is an important feature).
2) It might be easier to just position the IK targets at the same position as the feet when they need to lift off of the ground. That way you won't need a weight parameter any more and the slight performance impact can be avoided.
Rotation limits are currently on the to-do list, along with pole targets. I will most likely try re-use the bullet constraint component for this purpose.
I'm a non-binary non-cis sexually fluid cephalopod identifying genderqueer mocha frappé latte