From the developers, all that is required is:
- to link a set of levels
- a way to display story text and images inbetween levels
- a way to save progress (level passwords maybe?)
That is a lot less effort to code than it is create than a cohesive, well narrated story, balanced maps, and polished units.
Additional features:
- way to display dialog when playing, will come with lua scripting, surely
- improved AI? can wait as will come with time anyway