I had a high top GMC full sized conversion with the powered rear bed and swivel captains chairs...loved that van, hated the MPG.
That being said, the downfall to the swivel seats was that they had weak support in the floor, they "rocked" back and forth ( flexed the floor steel ) enough to make my wife uncomfortable on trips when she'd sit in back. The rear "bed" was a PITA as the motor was weak and had to be helped to move, and there was no rear switch, so it had to be done with 2 people ( one on the front switch, the other person "helping" )
The conversion van in Astro Form I saw had nice buckets and a manual bench/bed. You could manually slide it forward for more cargo space, and also to drop it into a bed, it could be adjusted to fit in the van in the best manner possible. I liked that aspect of it. Didn't notice if the seats swiveled or not, I don't think they did. How about the split bucket seat bench rear facing? Install mounts so that it can be put in backwards, along with a table. It would probably be less work or the same to swap the seats around, more stable, plus you get the extra seating for another passenger to boot! I was actually thinking about seeing if I could pull that off with my van.