That vespa and that cannon do not look survivable if para-dropped. Also an artillery cannon with no-recoil ? How would that even work on a Two-wheeler like a scooter ? Im pretty sure you would have to dismount and re-assemble the cannon on solid ground.
Despite the name, it is rare for the forces to completely balance, and real-world recoilless rifles do recoil noticeably (with varying degrees of severity).
A Vespa cannot take that kind of forces and survive.
No see, keyboard warriors intrinsically know more about military practice than actual military producers and planners. It's unfathomable these experts aren't provided with a job on military contribution boards.