Alt-fire: Spend 100 Metal to camoflauge a friendly Dispenser or Teleporter for (value) seconds*
On hit Spy with alt-fire: Breaks his disguise and/or decloaks him, showing him who is the boss!
-20% slower upgrade speed
On hit Spy with alt-fire: -34 Metal

*Resetting a cloaked building's timer will have a reduced cost based on time remaining.

Thinking it'd be nice to have some tools to make stealth as an engineer a bit easier, though should also come at the penalty of not being able to upgrade your buildings as fast as other players.

the upgrade downside could be negated by other engineers tho

im not sure about it but heres my idea.

(-) -30% damage.

(-) -20% building upgrade speed

(-) -15% building healing speed

(+) on hit (invisible spy): splatters paint on target

(+) painted spies are marked for death

could definitely use some tweaking but the concept holds.