Fisher has come back well from his latest injury and bowled well for Surrey last season. He's a good choice. Of the Lions players: Eddie Jack, Josh Hull, Mitchell Stanley, Tom Lawes and Sonny Baker, I don't think any of them are ready to be thrown into an Ashes series. Hull is probably closest (and of course was picked for a test last year when he definitely wasn't ready), but he tends to be very expensive.
Saqib Mahmood should get another go, but he hasn't played First Class cricket since May and has had a lot of injury problems. He does have a central contract though and I hope he doesn't just play white ball.
A pity Sam Cook isn't off playing Grade cricket somewhere.