Exploiting? As long as the soldier is not capable of doing any movements that a human cannot, I don't see how anything can be exploited. If done right, controls can only be a limitation (if set poorly), never something that can gives you an advantage greater than you should have.
In any case, personally I don't like holding keys at all if it can be avoided, and change all key bindings accordingly (when possible) in all games I play. Sometimes I even wonder if holding the move forward key and hold breath key is a good thing (especially when default hold breath key is on the mouse), though with those I usually just deal with, but then again for Arma I made a macro to hold my move forward key for long walks/drives so I don't hurt my finger after playing for a few hours.
In the end, as long as there's a reasonably viable option for binding keys so I don't really have to hold anything, that's what I'd be using. Even if it means I end up binding every key on my keyboard to something (though hopefully I won't have to).
Edited by galzohar, 22 October 2012 - 12:39 PM.