I dont know how long Gene Simmons and his over inflated ego could compete with the demanding tour logistics with Axl
Gene does indeed have a massive ego, but I'd say his professionalism toward touring is what would prevent a tour with Axl.
While Gene Simmons and Paul Stanley get a lot of well-deserved flack for being rock n roll whores (for doing anything and everything for money), it is also a fact that neither Gene nor Paul will settle for anything less than a stellar, calculated, well-organized show.
Paul and Gene have said that they wouldn't welcome Ace Frehley back in the band anymore because of his erractic behavior, and how they didn't want to subject their audience to Ace's antics. If they wouldn't tolerate that from their founding guitarist, I couldn't imagine that they'd put up with Axl Rose's notoriously unpredictable behavior. Say what you will about Kiss, they are a machine when it comes to touring, operating by a certain standard and schedule. On that basis, Axl would drive them nuts. Gene and Paul wouldn't want the risks and liabilities that accompany Axl's stage shows.
On the subject of whether Kiss or Axl would play first -- Kiss would HAVE to play first, otherwise they'd be going onstage at 4 a.m.
Bottom line is: Kiss needs to tour with bands that are willing to live up to their schedule and performance standards. Axl needs to tour with bands that don't require anything other than going on stage first, playing, and then not needing to worry about what Axl does. Kiss and Axl would mix like oil and water.