I acknowledge your point. One who is Rimé is not supposed to jump around from lineage to lineage haphazardly, but rather have a firm basis in their primary lineage and maintain respect for the others and realizing their usefulness in taming beings with various capacities and preferences. Practice questions and discussion should most definitely be directed to the appropriate area (and more importantly, brought to the attention of one's lama).
That said, if one wishes to discuss some of the great Rimé masters, currently there are only the Tibetan Buddhism forum in general, a subforum for one of the schools (i.e. Nyingma, Sakya, Kagyu, Geluk, Jonang, Bön), or the subforums for the profound teachings of Mahamudra & Dzogchen.
As I mentioned before, these masters don't really fit into such neat categories. Take Kyabjé Dilgo Khyentse Rinpoche for example: he's technically Nyingma, as he was educated at Shechen monastery and several of his gurus were from there. But one of his most important gurus was Dzongsar Khyentse Chökyi Lodrö, technically a Sakypa (though also a great Rimé master not easily pigeonholed). He also was both guru and student to many great lamas, including HH the 14th Dalai Lama, who said that he'd received important transmissions and empowerments of all the schools from Dilgo Khyentse Rinpoche.
Discussion of such figures would, to my mind at least, be facilitated by a Rimé subforum. Simply put, not all of us check the forums for all the different schools, for the same reason you indicated---wanting to have a firm basis in the lineage we study and practice. But more people from all schools would be inclined to check the Rimé threads in appreciation of the great Rimepas past and present, rather than having to search high and low through the various schools to see where these figures happened to be classified under...
Perhaps it could help break down some of the barriers we artificially construct around our "solid" identities as practitioners.
"The Sutras, Tantras, and Philosophical Scriptures are great in number. However life is short, and intelligence is limited, so it's hard to cover them completely. You may know a lot, but if you don't put it into practice, it's like dying of thirst on the shore of a great lake. Likewise, it happens that a common corpse is found in the bed of a great scholar." ~ Karma Chagme དྲིན་ཆེན་རྗེ་བཙུན་བླ་མ་རཱ་ག་ཨ་སྱ་མཁྱེན་ནོ།