But I am asking that we focus on the mechanic here, not the motivation.
Sure; I've said it plenty before. Affinity is awful, because it stems from a time long-gone where Divine teachings presided over the city states. Nowadays all it really does is stifle inter-circle interaction (that isn't to do with enemying) and limit RP even further than it already is.
I know you said not to mention motivations or anything, but I will say this... If affinity is to get changed, it shouldn't be in a way that benefits the aformentioned attitude (let's be real, a lot of classleads get made purely out of spite--this is directed at nobody in particular, just stating the obvious). Imperian could sorely do with lessening the effects (or removing, either works) of horribly outdated mechanics that don't really belong in Imperian. Lore is an irrelevant point, when the lore reasons behind affinity don't really exist anymore.
eta my own thoughts: I personally don't think there's any reason for keeping it. From what I've gleaned, the only real argument is there being powerful profession combinations... There's powerful inter-circle profession combinations, certainly. There's equally powerful intra-circle profession combinations as well, though. Classleads are used to balance outliers; it shouldn't be a factor really.