Javolenus, the 'units' part of your question should be possible, but would require spending some quality time with the editor. You would have to create your own mod/scenario, wherein you:
1. Define your custom units
2. Create Action Cards which would field these units once played
3. Code the events which deal and execute these action cards
In my mind, having the PPs of the Action Cards set to the equivalent production cost of the unit would really be no different than producing them from scratch. Also, you might want to create events to subtract appropriate raw materials when the Action Cards are played. The only issue I can think of off-hand is finding a way in the editor to designate the (X,Y) of unit placement if you're designing a mod.
I really dig creating units from scratch, though. It's one of the many things I love about this game: I have unit templates in my head which I have to plan production for. However, I do think it'd be kick-a$$ scenario/mod to tweak the editor to have cities only produce PP & supply, and have to use this method to field your forces ...
Re the 'Order of Battle' part of your question: OOBs are never pre-defined, but is an in-game function to summarize your units and hierarchy of command; it changes as the game progresses. If you were creating a scenario, you could of course create/re-assign units as you see fit, but I'm pretty sure that's not what you're asking.
Hope this helps.