A flex face normally requires a reinforced cabinet to handle the stress placed upon it by the tensioned face, unless you use a retrofit kit. A retrofit kit uses a frame that carries the tension of the face. They are not cheap, but they work great. You can do a homemade frame of welded 1-inch square aluminum tubing, but it won't take a lot of tension and it will need middle braces to keep it from bowing inward. The faces will be floppy, not drum tight. And you need to add the middle braces in a way that doesn't create shadows. I would not try it if you have not done it before. And you will need to fab new retainers. A lot of work.
If you are looking for a way to give the client a cheap job, he could strip the acrylic faces himself. I'm not sure what you mean by "beat down," but if the faces are not cracked, and they are actually acrylic and not polycarbonate (Lexan), they can be customer-stripped using a lacquer thinner. Stripping polycarbonate is more of a problem than stripping acrylic, since lacquer thinner melts polycarbonate.
Warn the client that the acrylic may crack during stripping. I don't strip faces anymore—it's not worth the hassle to me—but if the client can get the plastic clean, then all you have to do is re-letter.
Really, the easy button here is to replace the plastic. Use the old faces for a cutting pattern. If they are pan faces, they should be replaced with pan faces. Replacing pans with flat plastic will likely show the lamps and be more prone to blowout unless you add hanging bars.
Good luck, and have fun!
Brad in Kansas City