The problem is, the deal isn't finalised yet and is still being negotiated - a good reason to swell Forpen coffers maybe. Don't forget though, that (subject to confirmation), the Rights that you have accrued at the time and point the pension changes will be ring-fenced. So, although you will have to endure 2 years worth of the new deal if you elected to leave in 2017 (assuming the new deal starts in 2015), the remainder of your pension will treated iaw your current terms. Might that be palatable enough?
I don't know what your employment rights would be, sorry.