[episkopos]

The idea of something that diverts both friendly and hostile projectiles, or something that randomises projectile trajectories, or anything in a similar vain, could be seen to contradict the idea that a team should never be better off without a given player. I would be very careful with anything which could affect friendlies negatively. I like the magnetic disk idea though.

How about a remotely activated force field around the SG which vaporises projectiles and lasts for five seconds, then takes ten seconds to recharge? If the engi spots a nailgunner, he can hit the force field button so he has time to get to his sentry to wrench it before it's destroyed. To encourage sensible use, the sentry's rockets could be disabled and it could do only 75% of its usual damage while the shield is active.

Or what about making SGs regenerate health fairly quickly, beginning five seconds after last taking damage, or even as Bridget has suggested in the past, making them repair themselves after they're destroyed? Maybe after destruction there's a five second period of smouldering and then during the next five seconds repairing noises are made, after which the sentry gun is restored with 50% health and a small amount of ammo. If it takes damage at any point during the auto-repair, the timer resets. The engineer can speed up the process by standing next to the remains of the gun. Maybe allow scouts and spies to deactivate the repair mechanism by standing on the remains for a couple of seconds.

Also, make the wrench and dispenser heal at 33%-50% the rate they give armour, and the medkit give armour at the rate the wrench gives health.