The air-bag suspension is part of the fork, so the fork would need to be replaced. Cruzbike sold the final iteration of the S30 with an unsuspended fork.
I had a Silvio 1.5 (they were dual-suspension) for a couple of years, before buying an S30V2 frameset in 2017. The front suspension on the 1.5 didn't seem to make much difference, and I don't really miss it on the S30.