In wall ac unit for grow box?

In one of my buildings I have a pretty large ac unit mounted in the wall that vents to the outside. The unit is about 5-6 feet off the floor and has variable heat and cool temp settings plus a switfh for vent/recirculate. I was wondering if I could just build a 4x5 box around it and up to the ceiling and use that as my only source of air/exhaust. I will be running 1 600w hps, some small fans to move the air around and 2-4 plants.
Any thoughts?

Have you looked around outside the window/is the exhaust close to anyone else's window cos in flower you might have smell issues since that'll be hard to filter. Otherwise I can't think of any real issues with it you just gotta make sure that the air coming through it is clean because you wouldn't want crap flying into your grow from inside the ventilation system. Ive got a pretty small ventilation system going myself and I'm growing 3 plants in one tent and 4 in the other and it seems to be working so I'm sure an ac unit will do fine honestly

It's in the middle of 8 acres and the surrounded by cattle pastures so no worries with smell. The air blows through the condenser coils but maybe I'll put a furnace filter in front of the unit just in case.
Thanks