DCS stands for Digital Combat Simulator so the main focus is combat. It could be interesting to drag fans from FSX or similar civil sims to make the most out of the outstanding DCS simulation engine and flight modeling. However, that may work for single player not in multiplayer. Generaly speaking, people do not accept getting shot down by fighters while on bombers let alone civil planes. Hosts could restrict type of modules they want to allow on their servers but that would deny the mission the magic touch of DCS and its great potential: Simulation of a true air, land and sea virtual battlefield.
They still can fit into the mission if they have a fighter escort, within a SAM unbrella and tasked to bring the President back home safe