Should it happen?
Yes.

If two athletes want to challenge themselves, why shouldn't they?

The genesis of the UFC is all fighting styles against each other to determine the winner. The perception of MMA being the most formidable style developed out of these fights to the point that everyone is pretty much running the same training these days. Maybe Anderson Silva whips out some surprise Aikido here and there, but the style is largely hanging out on a plateau.

So, yes, there is no better time for a boxer to face off against the champion of TWO UFC weight divisions to see if the UFC can still claim MMA superior to boxing.

I'm so there! And may the best fighter win!