Hello there, and welcome to OFPEC!
A working "RTS"-styled gameplay is something that many people have tried in many different places. There are plenty of MP-only games like that, known usually as "CTI"'s (Capture The Island), as an example the KPCTI. Another is Karillion's RTS IV, which likewise uses various elements from Real Time Strategy games, and is played entirely on Karillion's Bootcamp server.
As to the mission itself, you have two options (which can be combined, of course) here on the boards: One is to create a resource out of your system, and post it on the ArmA Editing/Scripting Resources Beta testing
board, where it will be tested and evaluated entirely on the basis of the scripting, and perhaps eventually added to the Editors Depot. In this case, you don't need any "storyline" or briefings or whatever, just the editor-accessible mission with only the most necessary scripts etc., to showcase it.
Alternatively, you can post the mission in the ArmA Missions Beta Testing & Submission
board, where it will be reviewed as a real mission. Your system will also of course be played, but the important thing here is perhaps more how it plays and how it works, what your objectives are and so forth.
Maybe for a start you could post it as a normal Mission, and then based on the comments from beta testers, you could turn it into a proper resource that can be submitted to the depot.