There is a complete listing of switchmove animations in the Ed Depot under tutes - references. It may be that you just have to try a whole bunch until you find the best one. There are several kneeling and crouching animations, one of the medic ones might work.
Note that some playmoves don't work from the init line and others require the unit to be in a particular state (eg weapon on back, or weapon not on back) to work.