Honestly as far as the main spinner goes I'm happy to see the Bashir experiment play out.
County cricket hasn't produced a good spinner since Swann around 2005. The theory of getting the best young kid and just having him do an apprenticeship with the test team, playing on wickets in India, NZ, Pakistan etc. being with the best coaches every week and playing against Test batsmen in the nets for a few years and seeing if he can develop into a test quality spinner is worth a punt. He just turned 22. Swann got his test debut at 28, Lyon 24, Ashwin 25.
It's not like we're losing out on some incredible bowling performances by sticking with him over Cook, Dawson, Leach etc. If Ahmed or Vaughan, Coles, Hartley start taking loads of wickets @20.00 in county cricket then maybe you have to think about bringing them in on merit, but honestly I think if it was the 90's or early 00's people would have just accepted the Bashir plan, waited 3/4 years to see if it works and not felt the need to turn every selection into a referendum on it.
I think Jacks has been picked just as a batsman who can bowl a bit for this test. No one expected a frontline spinner to play this test and Australia wouldn't be playing Lyon if not for their injuries. The 4 seamers should get 20 wickets and lengthening the tail strengthens Englands strength, the batting lineup.