Len/Ned ......I had considered the same concept and concluded it would be preferable for the rotating aperture/hole disk to be mounted on the discharge side
The fan electric motor will labour when the discharge is momentarily blanked as the fan is a [FAD] free air delivery displacement device ...not a pressure pump....however the frequency of closure [back pressure] should not be an issue
At the same time the smoke [water vapour mist] will densify
.......however hopefully not to the point where it condenses
An interesting experiment ....
Would the disk be rotating at say ~~200 RPM?......a small DC speed controller for the discharge disc motor would be most advantageous
A blanking disk with two aperture/holes @ 180 degrees.....one full size & one at 1/10 size?
Lots of variables
Derek