We just ran a fairly similar gametype this past Saturday w/ 3 flag stations. W/ the cold & snow plus lower attendance, the winter scenarios are kept a bit simpler than warm weather games. What we did was have 15 minute respawns, at each respawn rocket the score was taken as well. So if your team had 2 of the three flags up at that interval you got 2 points, the other team one. This was a day long game, 6 hours total, split in half (lunch in between) w/ different flag positions each half. So 15 minute respawns was ok for us - obviously it wouldn't work too well for a 60 minute game. You could certainly shorten it to a 5 minute respawn w/ scoring at the same interval - then maybe a rolling respawn for the last 5 minutes. Or, if action slowed at certain points, declare a rolling respawn for the next 10-15 minutes.
If you are looking for another idea (I just answered a similar topic on a another forum so basically copy n' pasted it here): A mission we've run during a scenario that could translate to a stand alone game type was kind of like a linear attack and defend. As I'm unfamiliar w/ the type of field you have, size or layout, this game would work well in a wooded area along a trail, or at least along a logical path thru your field setup. This was used for a Blackhawk Down scenario a couple of years ago as a "Mogadishu Mile" mission. It was used again this past Summer for a GI Joe vs. Cobra game & was honestly the most fun I've ever had over a 90 minute timeframe during a scenario. The instant-moving respawn we used makes for non-stop action.
As attackers you move along the trail dropping flags at predetermined points while defenders of course... defend. The respawn points are the flag point to either side of the current objective flag. See my rudimentary diagram below

...
Start of game:
X --->
O --->
O ---> O ---> O ---> O --- X
X = Attacker start of game position & first respawn
O = Objective flag
O = Defender respawn
---> = Flow
After the first flag position is taken by the attackers, everything shifts forward as follows:
X --->
O --->
O --->
O ---> O ---> O --- X
O = Attacker respawn
O = Objective flag
O = Defender respawn
This continues down the line until the last flag position is reached:
X ---> O ---> O ---> O --->
O --->
O ---
X
O = Attacker respawn
O = Objective flag
X = Defender respawn
The game ends when the time runs out or the Attackers take the last objective flag or "O" in the diagram.
The number of flags is up to you, I think we had something like 6 or 7 flag points to go thru. Again, our respawns were instant to maintain the high level of action, but that could be revised to however it suits your field/players, I would say though that a numbered respawn would be an ok alternative, but a timed one could be disastrous for the defending team. For each flag station they just used a construction cone w/ a flag in it, the attackers only had to pull the flag to make it their current respawn. This game type certainly can appeal to aggressive players as more than likely the aggressive team wins, so make certain teams are pretty well balanced.