The problem is likely not the cost of the meal itself, as a comparison the numbers previously published when LH went BoB show incredibly low costs for meals. More likely it's the unions and, due to hot meals not having been offered for a while, there now being aircraft that would not support prepping hot meals (ie. no ovens). And this is something that is especially a problem for AF, they seem to suffer much more at the hands of very strong unions that at times seemingly try to run the company into the ground. Offering a choice of hot meal, preselection up to 48h, for minimal cost is absolutely possible (Look at Aegean doing it very successfully while their fares are half of AF's!) - but it does require an environment that allows this.

I'm too of the opinion that the business soft product lacks, with AF and especially KL, and I too am absolutely interested in paying for business class if the product and price is right. Though in all honesty, AFKL would need to improve on both counts. When *A allows me to upfare most flights from Economy to business with a 100 euro premium, and on top of that offer a better product - then AFKL would need to match their product/benefits/price to a certain level for me to book that instead. Getting business class XP's goes a long way in this too - and could well be a deciding factor.
I don't expect that changing Gold benefits would be an option if that conflicts with SkyTeam rules for Elite+.