Speaking of lightweight RC Pullers, our team recently built and implemented one with only about four pounds of weight left to spare at the end of bag day. The entire subsystem weighs in at about three pounds (motor controller and wiring included), and uses a spool to retract. It can pull two RC's in auto within about five seconds, and could probably be sped up to pull within three seconds. I'm happy to provide further details if anyone is interested.
Here's a very preliminary video of the system in use at the Montreal Regional. It has become much faster since, and we now use it in autonomous mode. Skip to 1:15 to see it in action.
https://www.youtube.com/watch?v=pnUju-lFhRE