So for similar situation I have made a special cart using foldable scaffold and big tires from harbor freight so I could use it with big and long but not very heavy stuff. So just make a shaft truth the two front legs and install the two wheels not too low so no need to extend the back legs you can cut the front ones a bit than make plywood deck on top of the scaffold with the desire with and make something to secure the jet like the Velcro stripe than make some handles so you could use the platform as a wheelbarrow ,maybe sure that the plywood is skewed to the scaffold,load the jet on the deck and go ,this should go backwards up the stairs and truth doors,maybe this will help.