Funny that folks still want to Spey the Phantom, because in the real world it did absolutely nothing positive
for the airframe.
Not strictly true, actually: the Spey Phantoms had more thrust for take-off and better throttle response from low speed for a go-around, which were important considerations when operating from the much smaller RN carriers. Fuel consumption and acceleration were also better, and the Spey provided more air for the BLC system which lowered the landing speed. Of course, the high-speed drag penalties associated with the conversion were an unanticipated handicap....
As I've remarked elsewhere, if you wanted a low-risk, clean-sheet-of-paper, all-British, twin-Spey alternative to the Phantom, in a similar timeframe, you might well end up with something that looked very like the JH-7. I intend to build such a thing at some point.
For a "Chinese A-7", how about starting with a J-7 (MiG-21) shape, giving it a bigger intake and a Spey (converting an actual J-7 is probably not practical due to the Spey's diameter), and A-7-shaped wings for increased warload at the expense of top-end speed? Perhaps, model-wise, you could start with a late, big intake MiG-21 then fit it with the earlier non-radar centrebody to get the neccessary intake area?
