to pick up a custom power up if and only if I pick up a certain weapon? For example; What I want to do is make it so when I pick up the sword on the map, I turn into this ungodly beast, impossible to stop, but it only spawns once. And I want whoever to pick up that sword inherit those traits.
Place the custom power up directly on top of the sword, and make each spawn at start but never respawn? Flaw is that you aren't required to get the sword. But, to get the sword, you have to get the powerup.
I honestly can't say I'm certain about this, but in Halo 3 having the sword made your reach almost double. What you could do is place spawn the player in a hole that is just too deep to jump out of. There is a crack in the wall of the hole and a CP is just out of reach. Now a sword would also be conveniently located down there. Essentially this would force the player to grab the sword to get the CP which could then alter jump height making them able to leave the hole, then set weapon pickup to no so they would have to keep the sword.
Most people will want to pick up a sword. Just set the Custom Powerup to active time of 3 sec, and respawn of like 5 to ensure that it respawns frequently in case somebody misses the pickup.
You could have a hole in the wall with a cp in it and a sword set to fixed in front of that so you have to pick up the sword to get to the cp. the only flaw would be that, depending on how far the sword is from the cp you could not pick it up when you pick up the sword.
You could make the powerup give them 0% weapon damage and like 300% melee or w/e you want it set at, than they'd sort of have to use the sword.