Just to expand on this point, I think it would be a very hard sell. Both were expensive to operate, becoming increasingly difficult to maintain and periodically on fire. With the Netherlands' step back from Indonesia, their need for any power projection largely evaporated. ASW, these carriers' raison d'être, could be achieved far more cost-effectively with the advent of ASW helicopters (CH-124 & Wasp in this instance) operating from smaller, more efficient warships (Iroquois & Van Speijk), supplemented by LR MPAs (Argus & Atlantique). That's quite a lot of developments to sweep away to get A-4s!
Even if both naval arms were offered a couple of squadrons of refurbished ex-USN Skyhawks, delivered with full fuel loads, free of charge, I don't believe there would be the will in either nation to retain their carriers.
I'm struggling to think what alternative there is (beyond those actually offered). It is a very niche aircraft. If the primary purpose of the programme was industrial rather than warfighting ability, would not a LIFT-type aircraft, perhaps a licence-built NA T-2A or the MB-326 have fit the bill? If warfighting was the name of the game (the G.91 is somewhat anaemic in this regard and I would suggest that in 60s Europe, the A-4 was as well) then I would propose skipping ahead to a NBMR-3 without the VTOL fetish and developing an A-7 class aircraft. Not necessarily the A-7 itself, although I wouldn't rule out a licence arrangement. Germany and Italy could do worse, though this is perhaps straying outside the scope of this thread!
I've discounted the French aircraft not because they weren't capable but because the French industry needed no kickstarting.
