I voted "yes", but I because there was no room for comments in the poll itself, I'll post a caveat here:
A person who is a CM should be able to be on the command staff of a scenario, PROVIDED that person is NOT one of the CMs for that particular scenario. Just keep the distinction between jobs during the scenario. If you're a player in any capacity, then you can't also be a CM for that scenario, and vice versa. I say this because in the past there have been problems caused by people who were both players/staff for a side and were acting as a CM at the same time in the same scenario.
As long as this separation of jobs and powers is maintained during the scenario, I see no reason to go through the administrative hassle of having a CM effectively resign from the CM team just to participate in a scenario, then have to re-up as a CM afterwards. In fact, having staff players with CM powers would be very advantageous IMHO. For instance, they could turn on airfields for their side in a timely manner when needed for re-ups.
I'm sure some folks will say that staff guys with CM powers will give in to the tempation to use them as cheats during play. To this I reply that EVERY player faces the temptation to cheat by breaking the many rules in each scenario that CM's can't directly enforce with various settings. Scenarios only work because people follow the rules when trusted to do so. So there's no difference between trusting us grunts and trusting a player who happens to have CM powers as well.