Conceptually speaking, a big raise or lower of the suspension to aid getting in or out, lowering to the curb like an airport bus for instance, is certainly possible. You’d use the same concept as an air bagged hot rod, where giant air bags completely replace the springs.
I’ve seen everything from formerly leaf sprung pickup trucks to early ‘shoe box’ Ford sedans ‘bagged’ as the hot rod crowd calls it. I helped a friend do his mid-90’s Chevy Impala Wagon 20yrs ago, before there were kits, it was a lot of work. Today the kits have gotten very sophisticated, engineered to ride real nice and at a certain height with say 80psi in the bags, then let the air out and change ride height 10” for instance.
I drove a '63 Caddy that a friend's shop did, with the bags aired up to stock ride height, it rode like being on a magic carpet, without being sloppy. When parked, you could 'lay frame' slang for 'lower it to the point the frame contacts the parking lot. They did that one 'right'.
Where concept meets reality however, there are no shortage of challenges. The biggest problem with a 4x4 van that’s only been lifted 4” like mine, is there’s the axle and third member to consider. I could never return mine to stock height if I wanted to for instance, the third member runs into the engine supporting crossmember. I only have 4” of suspension uptravel total until the third member hits the crossmember (I have bumpstops that hit first, but you get the idea).
The problem is, it’s not just a ‘add air bags’ deal, there are a lot of things to take into consideration when asking a suspension to move a long distance, completely changing the suspension design, a LOT of re-engineering to do. I could imagine spending north of $20k to have someone do something like this to an Econoline, as there’s no ‘plug-n-play’ solution that I’m aware of.
These guys have an interesting kit for the rear of a F450 and F550 that may be adaptable to an Econoline. It replaces the leaf springs with industrial duty airbags, locates the rear end with control arms and links, instead of the factory leaf springs.
Link Air Ride Suspension Systems - Stengel Bros Inc.
If not directly adaptable, then the concept at least. There sales literature mentions ‘Kneeling Ability’, which sounds intriguing for your situation. There’s some detailed pictures in the installation guide PDF
Kelderman also offers some serious air lift full suspension kits, they show an Earthromer built from a F550 cab and chassis fitted with air suspension.
https://kelderman.com/shop/
Interesting topic