if you're going to have a classifier in there, you might consider to just have the other filters be an input to the classifier. after all, it can be trained to consider certain inputs important.
Discussion
as you suggest the classifier could be trained as it goes. What if the filter is also client side, the user can train its own classifier to detect what it doesn’t like
some clients try hard to be intelligent, such as iris.to. but it spins the fan on my laptop too much. maybe a balance should be struck.
one of the reasons that Nostr appeals to me is how the protocol itself is fairly lightweight. some of the clients i come across could stand to be a little lighter too...