Big accounts are naturally going to get more cross-posts from others.

I don't think this is the case, except from small accounts. I have found that the larger accounts using the feature tend to cross-post the work of others. Then there are curation communities like @ocd who are only going to reward cross-posts from others.

Perhaps a solution of funneling back the cross-post's rewards to the original post (like Resteeming does) would be helpful for creators like me.

Maybe, but I think that a better solution would be being able to resteem own posts into different communities, but only cross-post someone else.