No! Not the least bit "NUTS".

"Image" is an absolutely vital part of all performances ...and even more vital, ...is the performer's confidence.

I cannot imagine that any acoustically transparent mesh screen would have even as much effect as the almost inaudible variation that must arise whenever a foam "popper stopper" windshield is slid over a the grille of a hand mic.

Speaking of which, such "foamies" may solve your problem in a much cheaper way.

If it's "basic black" you're after, these are the ones I arrived at for use with my Line 6 handhelds, as they're the cheapest I could find that both fit snugly and consist of urethane that's solid enough to last quite a while: http://www.bhphotovideo.com/c/product/331923-REG/Samson_SAWS1_WS1_Windscreen_5_Pack.html

Something you can't easily do in metal, however, is to have an "art-directed" variety of colours available ...and the US company WindTech do a fabulous range of colours and styles in durable polyurethane.

WindTech's extensive range of colours that fit Line 6 handhelds (the 1-5/8" size) starts at the bottom of this page and goes on to the next page (8) of this link: http://www.bhphotovideo.com/c/search?sts=ta&pn=7&N=0&Ntt=handheld+mic+windscreens

By the way, do Shure SM58 replacement grilles actually screw on to Line 6's capsule threads?

It's something I'd never thought to try, but if they do, not only would there be many sources of cheap replacements, but the sight of a 58 or beta58 grille would be a great "placebo" for checking whether or not some performers really can tell the difference between Line 6's modeling and the Shure originals.

Before the "hate mail" starts, you will see from some of my earlier posts that I am fully aware of experienced performers' genuine dependence on the exact proximity-induced characteristics of their "known" mics ...and I do always insist that their needs be met whenever possible.

(I do, however, "draw the line" at the contract rider that insists on red M&Ms backstage. Any person with the least bit of audio engineering experience knows full well that the BLUE ones yield a far more rounded bass response.)