Just off the top of my head, two ways I think WWE could improve its image to sponsors would be;
1) Hire an outside firm to do advertising for WWE. The internal marketing team WWE has tends to suck when it comes to marketing their product in a way that makes it look interesting and acceptable. Shit, 2K Games does way better WWE advertising than WWE does and they make kideo games.
2) Better writing. WWE's viewed as low brow entertainment because it's low brow writing that insults the intelligence of the average viewer. I fully believe that you could have a decently written wrestling show and it would help erase some of that low brow stigma.
Well imagine being a regular view of HBO and AMC type shows, and flipping on WWE RAW for the first time, featuring weird, stilted backstage segments where everyone stands shoulder to shoulder in a row, nattering commentary and people talking about "Superstars" and "Divas" in place of "men" and "women".
NXT doesn't have incredible writing by any means, but it does have basic stuff like continuity, character development, etc. Like they'll call back to a previous promo or match, even from a long time ago. It's not hard to keep track of this stuff.