> There's a problem with this though. These fans weren't designed to be run with a filter. The filter will restrict air flow which will put a higher strain on the motor causing it to use more electricity and in worse cases could be a fire hazard. The higher the MERV rating (cleaning efficiency) of the filter the more stress it will put on the fan.

I'm fairly certain the opposite is true. In fact, most rowing machines work on this principle. The easiest setting is the one where the fan is as closed off as possible because it's pulling a vacuum. Less air, less resistance, easier to row / less power required to spin the fan. If anything, fans should draw less current with air flow on the inlet side restricted.