Rob,
Re:
MGS fire its 105 over the side (gun perpendicular to the hull) - there was no issue I could see. I'd heard there were issues prior to that
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According to an eye witness, during the Saudi trials for LAV 105 system in the mid-90s, firing in this attitute caused the frame of the vehicle to warp.
As you say, they may have fixed the problem by now.

Doctrinally, the whole concept of 'tank destroyers', lighter armored vehicles with big guns, has always been problematic. The MGS was originally fielded in platoons of 3 vehicles, and an experienced armor NCO commented that all that arrangement was good for was TOC security, as the vehicles could not work in wing (two vehicle) teams. Given the intense 'infantry-centric" attitudes of the brains at work there at the IBCT (especially GEN Eaton), they may have envisioned tasking out single vehicles to support infantry companies or platoons, a concept that tankers choke on for good reason.

Actually, our language talking about this says a lot about the problem. The MGS is not a tank. But we don't have a clear designation for the folks who operate it. They'll either be disgruntled tankers who want a real tank or disgruntled infantry who want a real IFV (or to walk).