the sentiments of great masters such as Jamyang Khyentse Wangpo, or even Namkhai Norbu Rinpoche, and rather examine them and try to fathom their understanding
Please post some information about these 'sentiments', in particular any quotes which assert that it is okay for Buddhists to 'pick-and-mix' from Bon deities and practices.
Well, I don't have any references on hand, but maybe others will fill in. I doubt it is a "pick-or-mix" thing, but more likely the general view of the Rimey movement: practicing each lineage and/or transmission independently, according to it's own logic and system and seeing the value it holds from it's own basis path and fruit. Of course, only the great masters could do this with a great variety of lineages and practices, however, I am sure an average practitioner is able to pull this off with a couple. If the Bonpo Dzogchen is valid, which many Buddhist masters have said, then it is still Dharma, whether or not it is associated directly with Shakyamuni Buddha. Of course, mixing up practices from different lineages (assuming I am understanding what you mean by "mixing") isn't appropriate even within the same lineage. You must begin, proceed, and end each practice according to it's own form and not mix together two different practices.
Anyway, I don't choose to dabble in Bon and it may be confusing for others who do, who are Buddhists, however some people may have significant karma with both and find it mutually enriching. I won't be the one to make any grandiose claims about what is and is not appropriate for everybody.