Be careful with adding NPC's to the party. It's easy for the players to rely on them for everything... even thinking. An even more insidious trap is if the GM gets to attached to a pet NPC and starts running it like a pc.
For just two players, cop drama could be a good way to go. You have just the two main characters, plus you have supporting NPC's as needed. And only as needed. Having an organisation behind them helps with some of the burden normally borne by fellow pc's, no matter how understaffed and underfunded that organisation may be.