I didn't interpret you as saying that the F-35B should be cancelled. I'm more bringing context that it's not solely a US Marines toy, and not solely a baby-carrier plane.
I don't think that adding catobar support for modern fighter platforms is viable for all of these small carriers that are incorporating the F-35B. Admittedly my understanding of the situation is very shaky, but by all accounts I've heard, the catapults and arrestor gear place very significant strain on even the US supercarriers. More countries used to operate catobar carriers in the past (such as my home country of Australia, up until the retirement of the Melbourne and a decision to discontinue fixed-wing carrier ops), which I suspect has to do with the operation of lighter aircraft from the carriers at the time. (~7t max takeoff weight for a Sea Venom, ~11t for a Skyhawk; compare to ~30t for a Super Hornet or an F-35C.) Maybe the situation has gotten better with EMALS cats, but we're yet to see this technology used to make baby catobar carriers a thing, so who knows?
The countries in question would likely need to upgrade from their ~25000t LHDs to something with at least the displacement of the 40000t Charles de Gaulle. (Not to mention that most such carriers use nuclear power for both propulsion and to power the cats and traps.) Such vessels would come at great expense, and likely also have significantly larger crewing requirements, which tends to be a pain point for middle-power navies. I also don't think a lot of these vessels would've been built bigger in anticipation of catobar requirements, as they were largely originally specced for helicopter deck and amphibious roles. The F-35B really seems like an opportunity which all of these countries have siezed upon after seeing it come to fruition.
Again, it seems like you have a case with the Queen Elizabeths, though it seems like the UK balked at the cost of fitting catobar, if that's any indication.
As to whether the costs would've been offset by savings in the development of the F-35B, I don't even think we're talking about costs on the same magnitude here. For reference, total R&D costs for the F-35 as of 2019 were $71.9billion in 2012 dollars. Building and sustaining big boy carriers for middle-power countries would've cost the JSF partners hundreds of billions of dollars, easily.