I've never tried it, but I think that sounds reasonable. I've used ground mesquite seeds to batter onion rings; why not matzo?
Yes, it will just not taste very corny! And the texture may be a little less crunchy since matzo meal isn't as gritty
I would respectfully disagree. Though it will act like a breading, matzoh meal has a very distinct flavor that I, personally, would not appreciate on onion rings.