I appreciate the effort and love that people still invest time in RSS. I think that the hassle of manually defining and patching rules is n unnecessary burden. I tried to automate this task [0]. Sure the manual way might give you better feed entries, initially, but the maintenance is huge and ongoing. IMHO we should try to solve this problem in a more general way and by automation. With a post processing step, to generate a full feed, this solution would be unbeatable and with zero manual maintenance.

[1] https://github.com/damoeb/rss-proxy