Sure but these immunological effects are mediated by circulating D levels, which can be kept in a healthy range either with modest D intakes + high calcium, or higher D and lower calcium.I have trust in the idea that D is about Genomic Effects,controlling the controlling gene-clusters foremost,and that Ca-regulation and PTH are important parts in it,but that D is a general purpose Immune-Hormone,which is engaged in general purpose Tissue apportion,maintenance,structure-forming and Invader detection and Elimination.
As for sunlight, it absolutely does have very important effects on fertility, metabolism and general health, but I think this mediated more by melatonin suppression, dopamine and heat (infrared light), among other things, than by D. D is important in the context of low calcium, with high calcium it is less crucial although you still need some.
Yes I do think you need some D, but the amount depends on context like calcium intake and genetics. I'm still skeptical of the need to supplement unless you specifically grew up in a context of high D intake and moved to an environment with lower possibilities to get D.Why high of any of them? Why not just moderate? That would seem the best. You reassure you have vitamin D not just for its calcium absorbing properties but for its immuno modultory and gene activation properties. And you have enough calcium to supply the raw material for bone? Vitamim D is not only for bone health. Calcium has more functions than bone health aswell.