I'm not sure if this would be a way of cheating the system or not but I think it would be a good idea to allow Multiple Follow-Ups on dispatching calls.
For instance say you have all your units used up on a dozen calls, and you have a dozen more that you wanted to follow-up on and from there more pop up and you follow up again. Pretty much using units to follow up on two or more calls after its current one. This could be for all versions of the game.