Maybe but I am sure their are more ways to get around then you can reasonably defend. Besides spend too much time dealing with the light operative and you are giving the rest of the enemy team a easier time.
Honestly I will spent time just keeping people away from the objectives.
This. If anyone hasn't played Enemy Territory: Quake Wars (ET:QW) they should download the demo. It will give you a very good idea of how the team elements of the game will work.
Just... with vehicle combat added.
Soldiers blow stuff up, Medics revive, Engineers build and fix, and Operatives harass and hack/disguise.
But the main goal is to stop the enemy from completing the objectives.
Edit: I plan on playing Heavy religiously, so mowing down lights in cramped hallways is a specialty of mine.
Need a Light exterminator? Call Napalm Inc.
But really, I wouldn't be all that worried about the amount of people playing Light, because they will eventually figure the game out. Or they will move onto something else if they don't like it.