You're quite right, DD. Combat Mission, for example, has never spawned a workable campaign system as PBEMs usually take 4-6 weeks or so. Far too much slow down whenever battalions go bump! Somehow the 'Onion Wars' play on but I've not seen any other groups survive many encounters before burnout.
So, a PBEM campaign is likely to be a year's undertaking, perhaps. Alternatively, if you're in it with a few locals (or, at least, people in nearby time zones) then the resolutions can be quicker and the whole kept rolling along. A mate here in Melbourne has been running a French Revolutionary campaign for years using Empire Rules. He has the same issues in a way. The fighting with miniatures is a little like watching paint dry. Slower, actually, as they'd meet weekly and often have to run big battles over several weeks to get them done. Paint generally only takes a day! LG at least promises to get battles over in one sitting, even with half-a-dozen players, allowing the campaign to get going again. For a long time I've imagined that to be one of this games great promises.
@Gaz: I thought EiA was much more strategic in outlook. You've trimmed it down a bit in a campaign mode to synch with LG? It'd be a good idea to do a thread, I suppose, narrating the use of the system with LG once it's out, perhaps. I know you said you've worked on linking it with LG. Sounds very promising.
I understand that Cyberboard would be some work. Surfing around yesterday brought up a site that showed even a simple boardgame requires about 12 hours of construction. Still can't help wondering about fiddling with a version of the empire campaign rules adapted for LG. And, as mentioned, I believe someone has already produced a vassal to support Le Vol de l'Aigle.
As for OoBs, I've presumed that you'd set up a LG file of each side for the campaign, then just do quick edits for the troops at particular engagements, no?