I actually have played a game where it shifts between RTS and FPS depending on rank. Think it's set in a fictional semi-futuristic cold war. Really, really cool concept, but in practice, the FPS guys do not ever do what the RTS guys tell them to. We'd have to find a way to counteract that. Autoshot for desertion seems plausible, but might be a little frustrating. Maybe the RTS guys control a grand overview, where they can say unit 1, 2, and 3 go fight at vimy, which then leads to them having a realtime FPS battle there, while unit 5 and 6 go fight over a nameless hill with offmap artillery support. Just an idea.
or just let the general appoint commisars to execute deserters, dissenters, dissobediants, and dumbasses. Actually, mabye, have several generals who play a grand strategy game, with a set group of men to use under them to do fps battles, where they will be put in squads led by a captain, and ignoring orders long enough means a free RDM from the captain. Idk how, I need to get a game design document up, and that is going to take forever.