So you're saying that Isshin at some point after the vizards ascended all the way to captain level. Especially when bankai takes almost 100 years. We didn't see Isshin in a VC seat either. That's why I think if he left SS real early they wouldn't recognize Ichigo. He got put into a gigai at some point in the real world and started to lose his powers. Ichigo was born with shinigami power of his own and when he got stronger that's probably what awoke Isshin's powers.