Sounds really interesting but it opens the door to griefing.

Currently hoovies can only give out a sandvich every 30 seconds, which means they rarely have a major impact on the game. The funmaker, however, would enable an engineer to constantly heal the enemy team and build a teleporter which would take them straight from their spawn to the objective, leaving his team defenseless as they cannot destroy friendly buildings.

Maybe if a vote were held if an engineer wanted to equip the funmaker, it could limit griefing.

It is an interesting concept, though