OK
If you look at available drydocks in RN possession you can see why they would prefer an original limit of something like the Colossus Majestic during the 1950's.
Once you go beyond that a ship of about Hermes size is something that can fit a reasonable number of the remaining larger drydocks.
Now look at propulsion and again once you go down to a two shaft solution using UK machinary, props etc... you end up looking at a ship roughly similar to Hermes in size and/or displacement.
Hermes herself, could if need be used as a pure ASW ship, the retention of her as a nuclear capable for a limited number of Buccaneers is a product of the limited number of carriers able to operate the Buccaneer.
The Victorious question is a good one, the short answer is, it was convenient to dispose of her when they did, as she was the least cost effective of the 'moderised' CVs available and the longterm plan at this stage was to run on the remaining CVs (Ark Royal and Eagle), but not replace them.
CVF is, quite frankly the best outcome we could get and even now it's not certain we actually will despite the sunk costs.
It is true to say it could be better.
And it is true to say we could have had something not quite as good much earlier.
But neither of these options was going to make it through the tortured realm of politics.
