RTS Equivalent of A Deathmatch: Learning From FPS Games

Team Based Gameplay:

In FPS games, team deathmatches are very popular. In RTS games, gameplay is pretty much centered on single player campaigns, skirmishes, or 1 v1. 

The thing with RTS games though is that you are controlling a team instead of being in a team. It is more akin to being a coach or a team managers. There is no team of team managers.

Respawning: 

In FPS games, when you die, you usually respawn in most game modes. This lets off pressure to succeed.

RTS games do not have respawning when a player "dies". The closest would be hero units respawning in Warcraft 3, or having a builder unit like an MCV tucked away for a future base. 

How this can work in an RTS game is that players (like in C&C4) or whole armies can respawn (like MOBA creeps or how Art of War did it).

Different Loadout: 

In Call of Duty, you can choose which loadout you start with when you spawn and respawn. And that each loadout is more or less lethal as other loadouts.

This needs to be coupled with a respawn mechanic.

Comeback: 

When one respawns in an FPS, the player is still in more or less the same equal to their enemies. A respawned gun is the same as a spawned gun. An unspawned player may have the superior position, but in terms of potential lethality, it's still the same.

The ability to come back is paramount to an FPS success. RTS games arguably have the worse mechanics in order for a player to come back from a very precarious position.