I'm not sure if there are any muds out there like this already, but I thought it would be neat to a mud with a traditional Warcraft / Starcraft type of system.
But you wouldn't have to limit your game to just a strategy sys. For example: What if you could have your own kingdom, planet ? You would be the admin of the kingdom's economy, politics, army, everything. Upon creation of your Kingdom you are actually "building" an area that other players can traverse.
So, in essence, you start off as a player within a realm. Once you reach the level cap, you become a Leader, and then you start building for the mud, within the game. You can battle other cities, lead raids etc.
EmpireMud has alot of the kingdom building aspects, though at least in stock all the empire members (that fight, build, craft etc) are players. I have heard there is also a SMAUG derived base (Fear maybe?) that has kingdoms, though, I have not looked at the code so am not sure exactly what it does.
Maiden Desmodus has (two) kingdoms, mustering armies, controlling territory, etc.
I agree a strategy-focused mud would be fun. Assault is cool but it never felt that mud-like to me, more like a graphical game with a dense interface, kind of Dwarf Fortress-ish.
One idea I had for this was called Sorceror-King or something like that. Every player starts as a minor sorceror with a tower. As you gain in power you add land and minions to your domain. You can control these minions as units, or mob-switch into them to go exploring/adventuring/looting and so on.
While it seems like many of the more strategy-focused muds usually go to some kind of graphical representation like Assault, I wanted to try to stick to text reports of what's happening; I thought this could be a cool way to simulate ancient/medieval battles where spatial information would be somewhat limited by eyewitness/oral accounts and so on, and maybe a few detailed maps only accessible on the mud's website or something.
I played on the Assault Codebases in the later years that I remember them being up (Assault 3.0, maybe?) and I could easilly see them being modified to have something like what you have in mind. Well, easier than any other codebase I can think of out there ;-). There is another codebase I recall playing that was similiar to the Assault style of playing, but had less options but did include mobs. I can't think of the name, as I only played it for a brief time with marginal interest, but it'd be something to look in to.