It was never intended to be more than a temporary substitute for the FCS -- which will it now appears be tracked for cross country mobility reasons. It was selected because while not the best available vehicle it needed the least development effort and was the cheapest of its type. It was also selected to force the US Army to break the Heavy Division mentality (which may or may not work...).

The MGS was purchased to give direct fire support to Stryker units and it was emphatically not designed or planned to fight Tanks; it's a PC killer and bunker buster, roles for which the 105 is adequate. Here's a whole thread devoted to it; LINK

The Dingo, Bushmaster and Wildcat are different vehicles with different roles and do not have the x-country mobility of the Stryker. Stryker IFVs are armed with only a .50 cal instead of the 25mm precisely to keep the vehicle from being used as a 'light tank' -- which too many Brads get used for according to some.

Problem with 155s on wheels is you have to halt, emplace the weapon, expose the crew and then displace the weapon -- too much time and exposure; even solutions like the French Caesar and the Singapore and Israeli (and others) versions expose the crew. Only the Swedes have a wheeled 155 that does not and its too big for air mobility.