This building is a cheap, utilitarian building. It is ugly. But there are some simple things that can truly enhance it and make it beautiful in the eyes of the beholder. Establish the Tridentine ethos for the sanctuary to include the traditional set up of the altar.
Design areas for statuary that look designed rather than simply hanging statues on the wall.
A new paint job creating some contrasts with some stenciling, not a lot, would help.
Changing the harsh lighting system for something more subdued with spotlighting for the altar, tabernacle and ambo, would help.
Apart from turning this into a parish hall, what else would you suggest?