I am not a fan of spending money on the Invincible class to make it JSF ready when there are other current and relevant roles it can better serve.
I think the Invincible class is best utilized as an aviation platform for helicopters personally. It not only makes a perfect platform for testing future UAVs and UCAVs, but as a helicopter support platform the Royal Navy could put Longbows on target, which I think would make an enormous impact on how Navies deal with small boat swarms in the littoral.
With the addition of a heavy left crane, the extra hanger space could be converted to move some small boats for the SBS into regions like the Persian Gulf to operate along side RHIBs as fire support, and with the electronic suites and landing deck, it serves as a perfect Command and Control + Logistic platform for offshore naval activities similar to the purpose Ocean 6 currently serves around ABOT and KAAOT.
Just a few ideas. If I was Saudi Arabia, Brazil, or another nation heavily dependent on maritime security in the littoral for trade, I'd buy the ships of the Invincible class and use them for that specific purpose, although admittedly the Royal Navy could use the capability as well.