I might try creating this.

So far I know how to:

Replace models
Not control animations
Upgrading dispensers temporarily breaks the model and it has to be reapplied
Change the hitbox to actually be mini.
I can 'probably' modify how much it dispenses.
I /can/ modify whether or not it dispenses [metal/ammo/health].
How much damage it takes from any source.

Suggest me stats. The stats I like the most will be updated in this OP.

Current stats:

Cost to build and build speeds will be roughly scaled to be similar to the change from Sentry to Mini-Sentry. Basically see WeaponsofMassConstruction's post.

. . . pending decisions