In a riverine environment I think God/nature solved the problem of nitrates by doing a continuous 100% water change.Other than that, the nitrates are eaten up by the houseplant in the hob filter, like plants beside a river would do. All problems are best solved by The Master Engineer GOD.
If you like light-moderate stocked tanks with deep beds of coarse gravel and fish that don't dig, I guess the good old UGF still has its merits. I dislike gravel substrates, and hate having equipment in the tank, so they're not for me.
Sounds interesting what you're doing, I'd be interested to see nitrate and TDS readings for your tank though.