Interesting question. Anything is possible. However, I wouldn't pay the bigger bucks for a complete system from one of the custom fit vendors.
I have used the under dash "box" evaporator units that sell for about 1/2 of what they are asking for the custom ducted configurations. Most modern vans use remote evaporators so we know they will work. I see no reason why they couldn't be adapted to fit under the seat....there's plenty of room and the charge lines could be run under the floor for a very clean install. Under the seat you'd have room to fabricate your own ducting plenium...you could run duct hoses even up behind the seats which would keep it out of your face.
As for putting this system together....you're local automotive A/C suppliers...the guys who keep the A/C repair shops supplied with components (at least in my case) have all the necessary components "on the shelf" and have been very helpful in matching the components and doing the final crimps on the lines after I got everything plumbed in. At about 60% of what you pay for a custom "made-to-fit" setup it sure seems like a viable option. Interesting idea!!
Dave
