"Well, Reapers 'Jumping' wouldnt be a new Verb they would be able to do. It'd be an animation thing."
Exactly and this will help a lot in terror missions where small fences many time block Reapers to charge on your units.
"And Jumpjets seem like a crappy Flying Suit, and cant be implemented until Xcom has some notion of Gravity."
Correct, Jumpjets as high end stuff of terran technology wil be replaced by alien tech in Flying Suit. But that all depend how will look the tech tree and how fast you can reach Flying Suit. I have already seen jumpjets ability in "Incubation" game (which is xcom clone) and it was extremly useful there.
Aditionaly openxcom should have some gravity beginings since dead body fall to below levels when floor is destroy.