Attachable to Buildings

The Carrying Crate
Secondary: Building Attachment
Attach this to a building with M1. Press and hold M2: building becomes magnetic, attaching to friendly ally. M2 again to deploy item where the friendly unit is standing.

Meant to promote base mobility and lateral movement. The focus was meant to allow defenders to move teleporters between multiple defensible locations, especially on maps like Gravelpit. I'm still looking to balance this unlock better, as I think it promotes more sneak teleporting than lateral movement.

The Stinger

Secondary: Building Attachable

Attach to a building with M1. That building's usage charges a defending gun. When the building is not in use (not healing / teleporting / recharging) the gun will attack encroaching enemies.

Meant to provide wider base defense AND subtly encourage engineers and allies to move away from dispensers periodically.

The idea here are sapper-style items that replace the Engineer's pistol. He can then attach them to buildings to grant them unique abilities, to change his strategy, or offer bonuses. It's an unlock type that I would like to see explored because it's something I think hasn't been proposed very much in the past, and because I like the idea of extra buildings.

Some balancing thoughts: "friendly sappers" should not cause buildings to run counter to their primary mission: while the Stinger can open up new locations for a building, it shouldn't encourage Engineers to stop using their dispensers or teleporters as dispensers or teleporters. So I think the "friendly sapper" drawing charge from buildings functioning, not interrupting the primary building's function, and working best when the building is not in use are good strategies.

Post your own ideas for balance or attachables in the comments!