CDS has to be right man for the job
I do not have close knowledge of ACM Peach, but one thing I do know is that while still being politically aware single Service chiefs can fight their own turf (whether that is carriers for the RN, Army numbers post Afghan for the Army or whatever our 'red line' is). But when in the VCDS and CDS role the political nature of the job either results in a label of not being Joint (too much 'loyalty' to your own colour of uniform); not in the interests of Defence (you believe that your military professional judgement is better than the various studies, senior officer briefings, and civil servants providing you with advice), and finally there are those VCDS/CDS that historically just don't get that the politicians have their political agenda, inter departmental and cross party driving factors - the Minister's decision is to be loyally delivered!
Some take on the politicians and although it can be construed as good moral courage to stand up for the military against self focused, career minded politicians that rarely these days have served in H M Forces, but in reality these kind of VCDS/CDS just get bypassed by those that do have career aspirations and ultimately will do the Minister's bidding.
The challenge for ACM Peach, as he we'll knows, is to balance his light blue history and experience, with what is genuinely right for Defence, while ensuring Ministers (and his boss CDS!) are managed with a great deal of awareness.
That will determine his career future (and whether we can position a light blue CDS at the top of the shop) - not what brevet or cockpit he has previously filled. I believe that the position of CAS would be a sideways (if not downwards) move, and would certainly block us from positioning one of future CDS' via the CAS route.
Therefore I agree with previous posts being that our best hope is 'up' (to CDS) and not 'out' (when he finishes this job).
And I wouldn't write off the RN or the Army. The Army invest heavily in positioning its best at the top that shine with key crunchy jobs. SDSR 15 is one such 'opportunity' for the budding Army CDS, as is implementing Future Reserve 20. With the move towards contingency and not getting involved with long term boots on the ground, then the RN with its carriers are very well placed to lead Defence from 2015 into Future Force 2020.
But who knows and let's see what the Ministers have to say at the time!