Quote - the "industry standard" Foot rigging where the characters feet stay "pinned" but can slide left right and have a separate controller for heel& toe lift.

Hu? I must be missing the point somehow, I thought Poser already had most of that that. With IK on you can use the translate dials to slide the or lift the feet, and the rotate dials to lift the toes. The only thing it does not have is a way to lift the heel whilst keeping the toes on the floor. You could probably do that by making a new IK chain with the toes as the goal.
[edit]
I like very much shedofjoy's idea of a script to make  the foot parallel to the  ground, as this can be very time consuming.