Using Alice 2.2 (which also doesn't allow cloning/instantiation) my students had a similar issue, and solved it by using what they called "Megaman logic".

Megaman could apparently only shoot N bullets at once (3 or 5, I forget). Thus, they only ever had 5 bullet objects, iterated through a list to see if the bullet was shot or not, and only let you fire if there was a spare bullet.

I thought it was very clever. Sounds like you did much of the same thing.