OK, just had an IDEA for the door locks.....
Use a T-handle garage door lock. Then use the garage door mechanism that engages the sliding bars on your garage doors to connect to a couple lock rods...I'll check the local Home Depots and Lowes and give part numbers.
Basically, the T-handle goes on one of the doors. If you have both doors that swing out, one swings out/one in, doesn't matter, they should both work for you.
The T-handle goes on one door. From that T-handle, there is a bellcrank of sorts that throws a couple rods. One rod goes UP, the other DOWN. They slide in brackets (heavy corner irons or a couple chunks of drilled angle iron will do), so that when the T-handle is turned, the rods goes up (down) into a couple drilled holes (one in the floor/step, the other UP into another bracket)
If you look at a roll-up garage door from the inside, you'll get my drift. Just turn your head 90 degrees to see how it would work for the bus doors....instead of side-to-side, it would be up-and-down.
I sure wish I knew how to draw this out to post here....guess I'll make one someday and take photos......once I figure out how to get them from the camera to the 'puter, that is!