Go for it!
Chris,
Put back for pilot 6 months? At the age of 19? You do know that means you're not-not going to get it!
A 6-month try again means just that, come back and give it another go. The recruitment people love it if you keep showing an interest, but if you change your mind just because of a knockback then they'll probably hound you for it at OASC.
There is no reason why you can't apply for Pilot and put WSO/WSOp down the list - I got kicked back from all 3 days at OASC when I was 17 for a pilot bursary, then applied again at the tender age of 21 and here I am doing what I wanted. Stick to your convictions and desires and it shows some of that integrity stuff they love.
But if what you want is WSOp (role not guaranteed until on 55(R)), then good luck with it.
I recommend not saying in your filter interview that 22 Chinooks are the equivalent of 11 Nimrod MR2 and RAF Cottesmore! Have a look at the official party lines on the RAF website and read some newpaper articles rather than the rumour mills. You're entitled to your opinion (and expected to have them) but make sure you research thoroughly (The Nimrod MRA4 and R1 are quite different beasts - like Tornado F3 and GR4).
Good luck with your application!