I agree, there has to be some incentive for people to run standby delegates. It's difficult to keep updating/monitoring your delegate server, while have no chance being voted, receive 0 pay and forever be standby.
Also I agree there needs to be some criteria to be considered, the standby delegate must have:
* latest client version (most important, since this proves they are active)
* publishing feeds
and we can reserve some spots in the 101 delegates, just for randomly having stand by delegates start producing blocks. (or maybe keep the current 101 delegate limit, but add 10 more random spots, something like 101+10).