FLIR sucks. It would suck less if it could see through smoke.
Currently FLIR has very few use cases and too many limiting factors, like the limited uptime and forced low framerate. Outside of very niche situations in the day time, its basically useable at night only (and we know how often people vote for night maps).
In order to make FLIR matter in the day time and improve gameplay with it, I suggest that it gets to see targets through smoke. For balance and realism (which matters in block man battlefield to people for some reason), how far it sees through the smoke could be limited so as to allow smoke to maintain some of its usefulness.