Ultra thick and fluffy pudding
I suspect that their banana pudding, even if made from off-the-shelf pudding mix, was made with significantly less liquid than called for on the box. The whipped cream will lend looseness to the mixture even if the starch gel in the pudding is quite thick.



Note the cleanly-defined scoops taken out of the bucket on the left. That pudding is thick.

BTW, I don't think it's necessary or advisable to use much cream in the pudding. The milkfat will break up the gel, but you want a strong gel to maintain the texture. Likewise, while I see your motivation for stabilizing the whipped cream with gelatin, I actually doubt it's necessary because of the starch gel. I could be wrong here, though -- I don't have very good instincts for these complicated emulsions.