I like your idea for gradually getting him used to un-swaddling.
If you do need to use pd...here is what i would recommend for an older LO and what I do for pd: I put her down, if she gets up (stands or sits) I do pd again...a few times - once she stays down and is calm, I pat for a minute and say nap time honey, good night, then leave. If she won't stay down after a few tries, I put down one last time and say nap time, good night and leave. If she is upset (not just moaning or forcing it, but the very upset cry) I wait 1 min, go back in and repeat. If not upset at all hang back about 10-15 and give them time settle themselves.
He may surprise you and w/in a few days doesn't need you come back at all.