Change racial HD to +1 LA (which is worse to start off with, but would bring in the possibility of buy-off)
+1 to saves vs fear.
Burrow Speed 5 or even 2.5 (So they have to Double Move to go 5 feet in a round)
Intimidate added to the class skill lists for Ranger, Druid, and maybe Paladin. (Actually this one could perhaps work even without any change to the LA/HD mix).
Answers:
As a player I'd prefer it that way, if only to pay it off.
Simple and appropriate.
If you want it slower, say: "As a complex action which provoke attacks of opportunity".
I would include that in "Mepholk Alternate Levels".
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Strongarm Warrior: An actually worthwhile Monkey Grip-focused PrC!
Guyr Adamantine Avatar by Tomb Raven.