IMO, a 30000t STOBAR carrier would be the upper limit for a force such as this AU,otherwise it seems a bit disproportionate, the 23000t BSAC200 or an Invincible seem legitimate contenders
Since the Sea Gripen could be used on aircraft carriers starting 18,000 t, I will make a STOBAR carrier the size of the BSAC200, or modify the BSAC220 to a -200.
Edit: in this AU the 20,000 t STOBAR carrier is the replacement for a Majestic Class CVL.