To NigelWalmsley: Not a bad list, although on some level 2-5 feel like they apply to pretty much every rule in some way. 1 though definitely feels like a necessary, building up between the three levels/scales (I just made this system up). For instance your drive skill is used in action resolution which effects the chase which is scene resolution and if you catch the traitor you get information which feeds into campaign resolution. The trick now is to figure out what that campaign resolution rules actually look like.

I think giving stats to things that are bigger than the players would be a good starting point. Describe this city, that organization, the wilderness regions around them and whatever feels important to deciding how the campaign progressed. Then you need to figure out ways to use them, both within a level (If a city with 5 industry wants to improve its culture value, what happens?) and between them (If the heroes win a trial against the school of sneaky magic, what effect does that have?). I think I should work out some more definite examples at some point.

To Tanarii: Are there any quick resources I could use to get a feel for any of the systems you mentioned? Or any further detail on BECMI's systems that you enjoyed? Sorry this is all very open ended, I'm just getting started at this point.

To Vahnavoi: I mean my one example referred to armies. But the one I was actually considering using was based around provisions. I run a system with some survival aspects to it and I was wondering if I could encode how much longer you can go before you have to find another food source. Also it is a particular use case (and game system) that I can design for.