After a ton of screwing up and problem hunting, I believe I have a rather beautiful dispenser.
It can differentiate which team you are on, and if you're on the team it was built for, it checks to see if you're hurt. If you are, it heals you, then tells you when you're at full health. It cannot heal while being sapped, and will change colors/message colors depending on who builds it. It's probably the most complex thing I've done with events thus far, and I'm damn proud of it.
As soon as I make a few more toolboxes, I'll be reopening again.
EDIT: Finishing last sentry. See post below. I "upgraded" them so they're much more deadly now; they shoot more bullets and attack even when you're in the air over the usual bricks that set it off. In other words: Don't move in front of one for more than 3 seconds if you want to live.