Thanks everyone for the replies, excellent information and points all around. I completely overlooked the latency, that would definitely be a deal breaker for FPV. As would the on/off behavior of digital when the signal gets weak. In this particular case, these won't be an issue, and a range of 30-50' should be plenty. Also quality doesn't have to be top shelf, 640x480 and anything over 20fps should be fine.
The sole problem I'm trying to solve (and the purpose for considering digital) is to have paired TX/RX, so that if another camera system operating on the same frequency turns on nearby, the video from one system won't show on the others screen, as can happen with analog. It's OK if the signal gets bad and the video cuts out a bit, as long as video from one system doesn't show on the other system's screen. I have ordered some 8 channel analog TX/RX to experiment with, but for the final solution 8 channels won't be enough, there's too much chance of having 2 systems on the same channel in this particular setup.
I would love to hear of any digital suggestions if there are any, but assuming digital just doesn't pan out then I wonder if I can accomplish the same goal with a combination of low power multi-channel analog TX/RX combined with directional antennas? The cameras won't be moving quickly so keeping antennas pointed their way shouldn't be difficult.