For a variety of perfectly obvious reasons skill fade will be an issue. However, let us be quite clear, keeping a small number of reservists pseudo-current in VSTOL jets will not have any benefits whatsoever. If you want to operate cat and trap then that is the experience you must build and you must do it for a relevant cadre of pilots, i.e. pay for young pilots to get it with the two possible providers.
There are enough (very disappointed) stovies around to populate any unit set up to keep the fleet current without looking in the reservist locker.
If the new carriers are to be out of the blocks in 2018 and the oldest product we're looking for is a 40 year old Cdr (Air)/ Wings/ Air Boss then the oldest guy we should be looking for at the moment is 33. (Plus or minus years depending on how much wee you want Wings to smell of)...(then minus a couple for programme slips). Why on earth pay for post 38 reservists to fly anything?
And that's the bow wave, if you think that a 2018 F-35 'graduate' JP might currently be 18 and a non-grad as young as 15 you get an idea about who we should be giving hours to.
The two actual players in this game wouldn't dream of letting someone run the deck or Air Group without having flown cat and trap themselves. You also need big deck experience throughout the whole ship. So you might want to consider identifying the people who will actually matter as much as the pilots and get them overseas as well. Let's go for FDO (currently a non-selected CW candidate), CFD (a killick handler), cats and traps man, Wings (Air Boss in USN parlance), F (First tour rotary), little F (Shawbury or Linton), SATCO (Lt ATC at Yeovs) and DATCO (no yet joined up) as the barest of minima.
I am convinced that we have created a mountain to climb, but feel it would still be a considerable hill-shaped obstacle if we arrived at its foot with CVS/ GR9.