Here's a concept... I'm not aware of any current MMORTSs, most likely because I haven't looked for any. But here's my idea for one anyway... The game would be played using dedicated arrays of "battle servers" which would contain the distributed applications for running the game world and managing the data for each "army" involved (think Ender's Game [Orson Scott Card]). There would be "soldier clients" and "commander clients" hooked up to these battle server arrays and a single game might last several weeks because it would be spread out in little one or two hour shifts every day. A central mainframe of servers would manage each army and soldier's persistent data, and each army and soldier would have a budget, which would be tracked by a bank server. The budget allows armies to buy new equipment for upcoming battles or even for use in diplomacy. New equipment is constantly being developed by the project's equipment development staff and updated to the game world, battle servers, and clients. The game would also include a full array of mock battle servers used for training both new and experienced players. One thing about the gameplay is that it would encompass many genres. You could take the role of infantry and configure your client for a simple first-person shooter look or be an engineer and have an overhead third-person view. Or you could pilot aircraft or vehicles and have the appropriate flight simulator/driving simulator views for those, respectively. Soldiers who prove themselves as leaders would have access to the Commander clients, which distance the player indefinitely from the battlefield but give him/her a complete strategic view of the whole thing. The commander would give orders to platoons/squads in the field and the orders would show up on the regular soldiers' clients as overlayed arrows across the terrain or simply text messages sent to the client screens. A dedicated voice communications server would be part of each battle array to allow such in the game. Anyway, just an idea. I have nowhere near the resources to ever implement such a grandios idea but I might design it further and more detailed anyway. Any ideas and feedback would be greatly appreciated. EDIT: I might... might... might... attempt to implement a very simple framework for this as a proof of concept but as you may expect, I wouldn't be able to test that framework on my single-machine setup at home.

What you're describing sounds almost exactly like Planetside, SOE's MMOFPS. Most players are soldiers who can use different weapons and pilot vehicles, and those who earn "command experience" get access to a commander-style overhead view for issuing orders and whatnot. It's an interesting game but ultimately there is no "winning", the contested territories continually change hands.

As for an actual MMORTS, there is Time of Defiance, which is much more what an actual "MMORTS" should be, with many players in games that last several days. TBH it is just an RTS that takes a very long time to do anything :) But it is quite good.