Well it's like counter-strike
Your life is more valuable than your ability to do stupid things
Pros: tendency to be more organized games
Cons: tends to slow down to a halt, camping becomes prolific
There'd obviously have to be an incentive in that type of a game (like CS uses with hostages and bombs)
In a Halo game, powerups are one way to do that... Objective is another but it would require an overhaul...CS mitigates this by leaving objectives in multiple spots on the map. This allows offense to overload and defense to spread.
So imagine it's a one sided 2 flag or 1 bomb assault with multiple points of arming... It would essentially be CS
Hence why if it's legit, having the arena shrink down to force confrontation makes an elegant solution in theory to the issues of camping; you could be put at a disadvantage if you're scrambling to move at the last minute versus being active on the map.