Hey Robert,
this is a good idea which is only limited to how you affect the ventilation for heat dissipation of the controller. A temperature sensor inside the box would make sense then. Another way would be to enclose the source of the dust, e.g. by an enclosure like this or this (view of dust hose outlet here and here).
I have experimented for a while with filters for fans on PCs, but it turned out that they immediately limit the air flow and also clog too quickly (I have seen someone using such a clip-on fan filter on the (in my opinion too small) fan of the Onefinity Controller but I don’t think this is the right solution, especially not with such a small fan). My solutions since then have been to run the computers in large enclosures with a filter at the entrance of an air circulation system. This allows for a larger filter area and therefore better airflow and less clogging.
I think your idea is good.
PS: Note that with Version 5 of the Onefinity Controller, the power switch is now a push-button (with additional circuitry onboard) which replaced the rocker switch of the Version 4.