Those look very cool. If only they were upgrades. I'd like the remote control one, so I can "push up" the sentry's, still, they'd get hammered so badly from missiles.
I need a anti rocket or sticky mine deterrant.
Or an Auto-repairing Sentry
A mobile turret would be pure genius. I still think a sniper turret would be something to see, though.
As far as the dispenser goes, the alternate could be a short-radius force shield generator...can take more damage as it's upgraded, and slowly auto-regenerates the field strength. Whether or not it could be repaired via wrenching is debatable. It wouldn't have the benefits of health and ammo dispensing, but it would work well at keeping the sentry alive longer, or it could be placed strategically on the frontlines to provide some additional cover support. Obviously you'd be able to shoot from inside it. Furthermore, it should have that effect that doesn't allow demo stickies to attach to it. Also, it could automatically reveal cloaked/disguised spies that walk into it, but maybe that's stretching its usefulness a bit.