I'm thinking mesh may be too fine and cause a stuck sparge. A lab or chemical engineering site probably has more of what we are looking for in terms of hole spacing and diameter. If the holes are 3/32 on 5/32 centers in a commercial false bottom thats a fairly good open to closed ratio. I would try to find a strainer at a restaurant supply for the fryer grease of something similar to modify. I would try to put about a 2 inch lift in the rim so the edge goes all the way down on the full circumference and has a 2 inch dead space to allow the wort to accumulate without too much turbulence. I think unfortunately the "time spent to return on investement" on your effort is probably going to be a losing deal on this one. A one off false bottom is a tough thing to make. I am a die hard tinkerer and as a project it would be fun if I decided that I wanted to build one to see if I could, but a commercial unit is definately way faster and well engineered already if you want to return to brewing faster. Just some thoughts, since I am going to have to cross that bridge too soon too. Thanks for the thought provoking topic.
Bob