Immunization against non-spike proteins would probably be more effective as a CMI stimulating effect rather than a neutralizing antibody effect. Stimulating a CMI response would still mitigate disease severity and would be most relevant in people already vaccinated or infected (probably the latter mostly). It’s just a thought, and I’m no expert. I’d just like to see an intelligent evolution to immunization, rather than the same approach that was effectively used at the height of the pandemic, but that can have some serious adverse consequences. Those don’t seem nearly as tolerable now as when the virus was raging through populations. Frankly, impressions often matter more than science, and if the vaccine science stands still (and the FDA and CDC are populated by s lot of intelligent dinosaurs), anti-vaccine rhetoric will likely gain in influence.