There are a lot of ways it could go wrong, for sure. IANAL, but lots of small and large companies have and do navigate these issues. But I wasn’t talking about legally contentious content; this would be a work-aruund for stuff that’s expensive to cache, or stuff you just don’t agree with and so don’t want to absorb the cost out of the goodness of yous heart. Just continue to defederate if you have any doubt.
Anyway, it was just a potential work-around to address OP’s issue. I’m not a Lemmy dev and won’t be implementing it.