In my WZ experience, it turns out that this strategy only works against a) bad players and/or b) players who aren't using classes. I strongly discourage it.
Decent players, if allowed to live, will hold a transition mode force field for up to 2 minutes; I do it all the time on my Scrapper because people just try to CC without actually killing me. That lets me restealth, drop a bombardment on one console, and then harass the other console. And that's even after every other ally on my side is dead on the transition side of the force field, let alone all the time wasted killing those allies.
Here is a list of classes that really need to be killed because a decent player will be able to stop a force field opening. Heck, even an average or subpar player can use these classes to really mess up your transition mode offense.
1) Scoundrels: Evasion --> Disappearing Act is a nightmare for attackers. So is Flashbang. So is Freighter Flyby. So is Thermal Grenade. So is Sleep Dart.
2) Shadows: Shroud (Especially 5second Shroud) + Speed + Force Cloak is also a nightmare. Mind Maze is also just as problematic as Sleep Dart (although it is less spammable)
3) Sages: Fadeout Speed removes all slows/snares and grants slow/snare immunity. Good Bubbling can keep a team locked down for 6 seconds on its own. Force Wave has a big range, doesn't have to be aimed, and takes everyone off the door.
4) Marauders (don't know the Pub ability names): Intimidating Roar + Force Camouflage + Charge can really keep the attackers tangled up.
Just trying to CC lock these guys is a great way to get your offense stuck for 2+ minutes on a bridge. Just focusing offensive resources into murdering them outright gets you the bridge in 30-45 seconds.
Ultimately, it's a gamble. If you kill them, you have a much better chance of taking the bridge in a much shorter time. But then you won't get your awesome transition push against understaffed defenders on a door; everyone will have just respawned. On the other hand, if you don't kill the defenders in transition mode, you might be able to make a nice transition attack past the bridge...or you might get tangled up and waste a ton of time. The gamble is still balanced on the side of the first option, just because if you took the first door you probably have the resources to take the second door given enough time. Gambling on the second option can really cut into that badly needed time.
I state that if your Transition is halted, you should proceed to wipe out all Defenders. I stated the specific situation you allude to here:
"Transition Mode starts the moment after the first set of bomb doors have blown up. Transition Mode will stay in effect until either your team's transition is halted, or your team reaches the end of the map and arms the last set of bomb doors.
Examples of a team's transition getting halted.
> Your team arms the first bomb. It blows up. Your team transitions poorly and does not open the bridge before Defenders get to the bridge. You must now wipe out all of the Defenders in order to open the bridge.
> Your team arms the second bomb. It blows up. Your team transitions poorly and does not open the barriers before Defenders get to the barriers. You must now wipe out all of the Defenders in order to open the barriers.
> Your team arms the first bomb. It blows up. Your team transitions well to the bridge and opens it before Defenders can get to the bridge. One of your teammates does not know the rules of Transition Mode and he kills a Defender after the first set of bomb doors have blown up. Your teammates that have made it across the bridge already do not successfully arm the second set of bomb doors because the Defender that was killed has already spawned and stalls your team until the rest of the Defenders make it across the bridge. You must now apply your Attacker's Golden Rules in order to arm the second set of bomb doors because your transition has been halted."
So if the Transition Mode is halted, you must kill all Defenders; and then revert back to your Golden Rules.