Royalist, Sandie,
Perhaps I can help a little here.
it's my understanding (from a very reliable source) that fitting arresting gear to the QEC carriers wouldn't be simple, is on the very edge of being feasible, and prohibitively expensive.The situation might have been different in 2000, but since then these ships have been designed and completed on the assumption of 'no catapults or arresting gear'.
What then happened was that the spaces that were 'reserved' for cat and trap gear was given over for other uses - it's simply not practical to sail a warship around with great empty spaces in it. In the case of arresting gear, the spaces involved were very large, and have been used to house the extremely large mission planning areas demanded by the F-35 team.
Now, imagine you now wanted to install arresting gear. You take ALL the gear out of the mission planning areas and put it on the dockside. Fit the arresting gear. Now, where does the mission planning gear go? Right, just empty a few other compartments, install the mission planning gear and - you have got an equally big pile go stuff on the dockside from the compartments you've just emptied. And you've had to re-plumb all the power, cooling, data and comms services you put into the original MP areas into the new ones.
Repeat the above process about ten more times. Not simple, feasible or cheap. The time to do all this was 2000. Trying to do it in 2010-12 was a nonsense, as the team working the issues after the SDSR 2010 decision found. Trying to do it in 2017 would bee a nonsense on stilts. In my view. It's a free forum, others may disagree.
STOBAR options and Rafale. I seem to have said this quite a few times, but using a ramp to launch a conventional (i.e. non-STOVL) aircraft isn't especially efficient. In brief, a STOVL aircraft can launch from a ramp at below flying speed, but use both wing lift and vectored thrust to manage the decrease in rate of climb so that the aircraft rapidly and controllably achieves full wing borne flight about 1 km out from ramp exit. It can do this at just about max TOGW.
Conventional aircraft can't vector their thrust. With only wing lift available, their only option to manage rate of climb after ramp exit is by using pitch angle (assuming they are at max thrust). They also need to achieve a minimum speed for acceptable control, as they don't have the low speed flight control systems that STOVL aircraft have. (The BAES 'Sea Typhoon' project eventually had to admit that they would need to add a reaction control system to allow safe launch at forecast ramp end speeds). Ramp exit speed is directly linked to launch weight. Higher the weight, lower the speed.
This means that conventional aircraft flying off ramps have limited payload and restricted launch criteria. Look at any films and you'll rarely (if ever) see any external stores on the jets. The Chinese Navy even went public a few years ago to berate their own aircraft designers for giving them aircraft that had almost no effective payload. The Chinese are working hard to get more powerful engines fitted (I believe) - that will help, but not so much.
I have no doubt that a Rafale could get off a ramp. So could an F/A-18. But not carrying much payload. Just physics at work.
Hope this helps a little, best regards as ever to all those new to this carrier aviation stuff,
Engines