Vegan is the answer to what this should be.
I would say that you can be vegan and still be eating food that was shipped in on boats then trucks. Vegan would be a net positive for any switch from the conventional western diet, but I see the merit in focusing in on carbon footprint of the food in question. And as potentially silly as calling oneself a ‘regenivore’ is, it still conveys a message and invitation for others to learn about alternatives and things they might too value.
yeah i think vegans sometimes forget that veganism right now is still, in a global context, not a very prominent dietary habit and may not scale up particularly well or sustainably (especially since not every place currently has an abundance of food, much less vegan food). vegan actions, while ethically better, are also not inherently sustainable either–some vegan products are less sustainable than their animal-based counterparts for a variety of reasons.
So whilst you are right that transport does create lots of emissions it is still only a small percentage of the total. Any localy produced meats would have a higher footprint than legumes from anywhere. A localy based food system would be great but to get that we would need mass land ownership reform.
While you’re right that reducing consumption of animal products is the largest impact on carbon emissions, I think you can be vegan and still eat foods that have a significant carbon footprint, if you don’t also purchase local vegan produce.