I thought of the idea of making a different bracket that could mount the trailer. I didn't think of making an adapter plate though. Good idea!

However, since the original post, I've attacked it with the dremel and it fits nicely. Surprisingly, that thing is made out of a good chunk of metal (once you start cutting it, it's thicker than it looks!). I ended up carving out the areas where the frame hit the bracket, and then covered the bare edge with a little rustoleum and a slice of innertube that died.

The inntertube just keeps the hitch from chewing through the paint on the bike incase the hitch decides to rotate a little around the skewer. That's all. If the bracket does rotate, it'll run into the frame of the bike and just put the squeeze on the rubber and not my paint.

For testing, I stood on the bracket and bounced. It supported my 180lbs, so it'll hold the 30lbs of kid/trailer without an issue.