this isn't a specific weapon suggestion, but more of an overall suggestion for the PDA slot for the engineer
Instead of just affecting Engie's two teleporter build slots, the PDA should act as a mini loadout which affects all four building slots, for example:
Default PDA - Sentry, Dispenser, Tele Exit/Entrance
Jumpkit PDA - Sentry, Dispenser, Jump pad A/B
Medical PDA - Healing Sentry, Dispenser, Jump pad A/B
Flanker's PDA - Sentry, Mini Sentry, Tele Exit/Entrance
Grordbort's PDA - Goliathon Sentry, Shield bubble, Tele Exit/Entrance
(these are not actual PDA or building suggestions but are just representative of the idea)
This would allow for more customisation in Engie's kit and help justify the existence of the PDA slot, as currently just having the jump pad doesn't really do it for me