I've read the thread up to this point. Very interesting stuff.
However, I would like to submit an alternate solution to the issue raised in the O.P.
I don't know exactly what 30mm gun is being proposed to be fitted to this new MGS Stryker analog. Hopefully it won't be some shiny newfangled gun with circuitry and laser beams, because everyone knows fancy gadgets never get used properly.
My solution is simple, take the existing MGS Strykers, remove the 105mm gun, and replace it with one of these:
That's a 20mm M61 Vulcan cannon, it is mounted in nearly every combat aircraft we have, has been in use for 50 years, we have plenty of them to pass around, and it will shred any infantry or light armor it hits. Also note the complete lack of circuitry and laser beams! It's a purely mechanical killing machine, designed from the very beginning to be functional, reliable, and to blast apart anything it touches.
Just look at it.
It's beautiful.
Aside from the fact the M113 is old and needs to be replaced, I always had a soft spot for the old M163 Vulcan ADS. So why not take the gun from the 163, and strap it to an MGS turret? If you replace the bulky 105mm ammo with smooth, streamlined, linkless, 20mm rounds, how many could be carried? Enough?
EDIT: I had to put a spoiler tag around that picture, because I'm pretty sure it's classified as pornography around here