Saltydog made some good points about this puzzle being pushing obscurity to new realms.
I think that is inevitable, because we probably picked all the low-hanging fruit. "Ford's Theatre" (IV) was at the easy end of the spectrum, "Curiosity" (CXLVI) was maybe as obscure as we should get. Though I thought the "Cat & The Rat" (CXV) was unsolvable - there was an exact answer within minutes! I guess the happy medium is something like "Cooper Vane" (CXXIX), which even produced an outstanding pun.
The "Solvang Conference" (III) and again "Ford's Theater" (IV) were seminal, as they changed the early character of the thread and enormously expanded the possibilities.
As AlanK states, the event is the answer, and we had drifted away from that. Not that we have any rules...
Now I'll put on my Goldilocks hat and find one not too hot, not too cold - Just right!