I'm in the same place in my stepvan build. The van has two-piece French doors, but after I upgraded the driver's seat, one doesn't open very far, and with 4" of insulation, that might be a problem. Also, the more seams there are to seal, the less airtight it will be.
For that matter, how thick is the insulation in your build? If it's little to none, you have more options.
I had not considered a pocket door! Even though the front doors in my van are that style. I'd have to think about how to make the insulation work.
For now, my default plan (again, 4"+ walls) is to have the front door just be an insert, held in place by 2-4 latches on either side (only one side at a time, and there's a back door in case some joker tries to lock me in). Part of the reasoning is to use the existing double doors as the insert's outer paneling, for stealth reasons. But it might become a hassle to lift it in and out all the time?