I have a beast of a room, 450 sq ft, 14 foot ceilings. 4 supply grills on the floor, and an inadequate double return, placed 10 foot high.

I would love to add more return flow. The only way I can see it (without tearing up drywall), would be to use the minfridge/closet that is 1 foot off the ground. I would be easy to have someone attach a return duct to it, and put a grill on the closet door. The problem is the return would be at floor level, about 9 feet from a floor supply. The supply grill feels like it blows straight up, and I also have a ceiling fan on low, 24/7. In short--the supply is very close, but at least not pouring air directly where the return would be sucking in air.

Would a floor return significantly disrupt airflow/ be a terrible idea?