The ability to have multiple projects underway at the same time by the same factory type (construction, fighter, ordanance).
Ideally, though undoubtably unrealistic with the programming architecture, is a fundimental change to factories and project assignments. Assign the project (fighter A), by shown that XX factories are available for the project, assign X factories to project, by queried if this is an openned ended or limited run project, if limited set limit. Have the ability to modify how many factories are assigned to existing projects, pause projects(possibly making the factories available for other projects), cancel, etc.