Mark will never be able to play like he "used to could", so songs with fast, extended solos are not realistic. That said, with better preparation and more practice, there are plenty of songs that don't require that level of soloing, but still has fire and energy. Look at the song he wrote for the Bill Wyman show, for instance. Fun and hot! It's not Sultans level, but it still rocks. The question is, is Mark even interested in putting in the effort to be at that level? I'm sure he can if he wants to, but the older he gets, the bigger the effort is going to be.
A tour with a similar setlist to the current one, only maybe slower, and with an older, weaker Mark? Thanks, but no thanks. I prefer to cherish the good memories.