There’s way too many languages and dialects with way too many sounds out there for this to be practically doable. For foreign names some basic degree of approximation is desirable, but nothing more than that. In principle you shouldn’t expect or demand people to produce sounds not found in their native dialect (unless they’re actually learning the foreign language).

Besides, it’s not even odd for people not to be able to pronounce stuff according to the standard norm of their own native language, due to the dialectal variety within the same language.

As for names from within the same language, it could sound artificial and even condescending if you tried to go for a pronunciation not native to you. Bob is just Bob, no need to stress that he’s “American/British Bob”.