"But what if I don't sell to foreign nations, to other states, or to Native American tribes?"
Works for me, but the Supreme Court had decreed that if you sell to ANYBODY in dollars, you're engaging in interstate trade.
"I suppose then your idea of communities is that they be what I'll call right now "trade immunity" zones, where as long as it's intra-community, it's sans regulations (besides things like fraud laws)?"
Not necessarily. There's still your LOCAL government to deal with- and they can have all the regulations they can convince their population to follow. But certainly, some libertarian communities, like Colton, Oregon, will keep the regulation down to "Carry a gun with you at all times" and leave it at that.
" And only trade outside the community would be where, in a sense, "foreign policy" considerations would come into play/get factored into trade regulations?"
Exactly. In keeping with the principle of subsidiarity, in which the least competent authority has the authority, and larger governments can't countermand that authority.