Earlier today, I played with someone who made a really good point about the 60 second setup phase during cp matches – why not help the Engineer when you’re sitting around?
If you are on offense and not playing as an Engineer, you can switch to Engineer, upgrade his buildings, and then run back and switch to your real class at the last second. On a 12 man team, if you have 2 permanent Engineers and 10 temp engineers, you can guarantee a pair of level 3 buildings when the gate opens. All the engineer has to worry about is setting up buildings, and the rest of the team upgrades. By the 45 second mark, every building is maxed out, and that last 15 seconds, everyone runs back into spawn, changes class, and waits the last bit before the match starts.
On defense, you lose some time due to the distance from your spawn to the front gates, but you can still help. In that same team, the 2 Engineers drop teleporter entrances, then run to the front lines. The rest of the team upgrades those entrances to level 3 while the engineer focuses on his dispenser and sentry. Once the entrances are at level 3, everyone changes back to their real class and either runs to the front, or uses the now level 3 teleporters to port up there. You can even have a few other players go along as Engineer to help upgrade those buildings, and upon death, switch class. That second scenario is a bit risky, since you’d lose a few good defenders for the sake of some defensive buildings, but it can still be useful.
You just don’t worry about making any buildings unless you plan to stick as Engineer. Everyone else just focuses on upgrading. The Engineer only spends metal to make buildings, thus allowing him to make more buildings during setup.