Few years ago there was an attempt to start sorting FD drawings in a "type-oriented threads" (with content by various Authors included) instead of generic "FD Scale Aircraft" and "FD Scale Vehicles" (plus of course "topic-specific" ones). And generally I was very much against it (paradoxically, as the P-36 and Dakota threads You've mentioned as examples, were done by me), because generally it would create a horribly high (and 'un-navigable') amount of separate threads.
Reason for actually making separate "type-specific" threads for Dakota and P-36/-40 families (as well as Sheepster's Manchester/Lancaster/Lincoln/etc. thread) was that their content was REALLY, REALLY BIG - 111 files with 880 silhouettes for Dakota family, 52 files with 510 silhouettes for Curtiss family and 63 files with 195 silhouettes for Lancaster family. And they were made from A to Z as specific projects, whereas the Airbus and Boeing (and other) airliners were added randomly, by various Authors over extended time.
So, if someone would, for example, decided to do a major project, showing, for example, all versions and major users of B737 and post it as separate thread, then sure, go for it. And of course there is no rule forbiding Authors to post separate type-specific threads even for single file with single drawing, but by convention, the "FD Scale Aircraft/Vehicles" threads are default places to post things. But if You suggest that somebody should start separate threads for A310, A320, B737, B747 and so on and fill it with already-made content posted in other threads... then I'd say I'm very unenthusiastic about that idea (euphemistically speaking).
Besides, the hopefully-soon-to-happen creation of FD Archive on the mainsite will probably make that idea moot anyway.