For rules, I'd suggest:
Triumph and Tragedy (with its own thread here on LAF) -- which is pretty much designed for interwar conflicts. You can read about it in the thread near the top of the forum.
Arc of Fire -- a WW2 set which uses figures grouped into 10 man squads. It should handle the weapons available in the German Revolution. Vehicle rules are rudimentary, I think, but then the vehicles in the German Revolution were rudimentary. These rules are definately fun.
Disposable Heroes and Coffin for Seven Brothers -- another WW2 set that groups figures into 3 to 6 man fire teams. Has more detailed vehicle rules (Coffin for Seven Brothers). Has a WW1 variant.
Chain Reaction -- I forgot what the WW2 variant of the Chain Reaction rules is called. These rules also divide the figures up into 3 to 6 man crews and fire teams. The thing that is unique about these rules is that once a group fires on another group there is an exchange of fire until one group or the other is killed, wounded, involuntarilly suppressed, or voluntarilly stops exchanging fire. It's an interesting system.