Problem is the many varying degrees of "fits lore." Do you mean "doesn't blatantly contradict lore," "isn't explicitly contradicted in lore," "is based on stuff in lore," etc.?
That is, of course, a hard line to draw and it wouldn't be exact but it would at least help. For example; I am making my own new land, it's an island off the coast of Tamriel. I have worked in parts of lore through thousands of years of TES history, and my island and everything that occured on it
could have easily happened. That, I would could as lore friendly. It never existed, but it certainly could have, and it doesn't contradict any established lore.
However, some mods are blatantly not lore friendly. Macho man dragons, the Portal robot, Dr. Zoidberg mudcrabs, my little pony dragons, that kind of stuff. At the click of a button I could filter out all that craziness and have the, at least semi-lore friendly mods to look at.