SIBullets,
Ouch, I think I can see where the problems are.
1. Is the 54' "mound" going to be flat?
2. The base paths are going to be the real problem. I suppose you could cut the infield grass in 10 feet and use "baseplugs that are flush to the ground when not using that base. It is going to look funky which ever way you go. I think that is why those length diamonds are skinned. Another solution is to do what UIC is doing and turf-grass in the entire field. You could do only the infield. I'm sure it's very expensive but it would solve the problem.
3. Maybe it's time for the JR High to play "BIG"
BTW- Maybe contact the UIC AD and find out what they plan on doing with the infield sod. PM me and I can set you up with a contact there.