I think you might be overly concerned , as it was not too ,many years ago there was virtually only one 315 200TW tire, and now there are actually 3 in 18s -- Falken, Yokohama, and BFG ( I actually think I am missing another?) The bigger sizes are more prevalent now than just 3-4 years ago. The folks at Bridgestone, BFG and Falken were checking competitor tires at the Solo Nationals and I know Peter Calhoun at BFG said the requests for bigger 18s, 19s and 20s was the main comments he heard. At Hoosier the number of folks on 335s was insane ----- I needed a couple of used 315s and they were non existent, but 335s would fill a large trailer.
With the 200 TW rubber , as well as the Competition Rubber, there are actually more choices now, and the change with the 305 RS4 may have been a marketing change for Hankook and have nothing to do with Tire Rack?
Heck, you can get the BFG Rival S and the S 1.5 both in 315/18s and the 1.5s also come in a 305/19. Great tire that saw a ton of usage at the Solo Nationals on Pony Cars and those in the CAM classes.
You're probably right, I'm probably just biased and bummed about nothing in 285/35 anymore.
Sounds like jumping up to 305/30/19 is my answer. The 18s are still too short for me.