Super simple prototype but if it works… Very cool idea!
This is a very good start. It will have limited effectiveness depending how exactly wet the filament is though, as the diffusion speed of water in plastic is low and it takes time to get the water actually out of the center to the surface to evaporate. The few minutes a filament sits in the inline dryer might be OK for surface moisture but will fail with wetter spools.
I think the ideal system would be to have a dry box that the heating unit and fan blow into, but then feed the filament out to the printer through a “stove pipe” that acts as the dry box exhaust. This way you’re still drying the whole spool over time but then get that “final blast” to ensure the surface is as dry as possible. Make sure to insulate all walls such that you reduce how much heat you lose as the air passes through.
