Definitely better late than never!
The idle players are simply those not active. Their lack of activity would be the same regardless of if they were identified or not. Currently, we're in a period of transition and rebuilding, so it's going to improve. In our prime we've run 30+ players.
Generally speaking, try to avoid initiating RP with characters without players. You'd never get a response. Fae and I are actively working on the lists (culling them down) and hoping that we'll be functioning with invisible NPCs until a larger player base can be put together again. When it comes to ranks, we usually have a player handling playing the NPC. When it doubt I'm a good guess.
As for RP, you cannot play another person's characters. So you would control your own character until you hit a point where you need input from them, and then stop. There are instances where you might mildly power play, but that would only be done in cases where you had express permission.
I'd also much rather have questions coming out of my ears then having to fight with cleaning up a mess caused by someone simply not asking.