Stronghold/Knights & Merchants
Never played Stronghold, but K&M. It is based on the idea of settler with an expanded combat system which worked due to the formation system. But combat is really slow paced in this game and not comparable to modern really, fast paced PvP RTS games. I doubt that K&M will work really good in an competive multiplayer scenario, but I'm just guessing here, just played the single player campaign.
A strong focus on the (single) core gameplay is better then to support two "core"-gameplays. Many eco-simulations have a battle component (settler,civ) and many RTS games have a eco-system (star craft=>two resources , etc.), but all have a single core game mechanism, either eco simulation or battle. If you take the concept of e.g. a RTS game and add the "burden" of a eco-sim, then you are suddenly trying to develop two games in one.