14 /2.8 would be sweet. I like the photos I get from my samyang but at times AF is nice to have. But I have to admit it feels good when I get those great shots from my MF lens, because I know that I did it.
120 /2.0 OS would be useful
Then, although it should be put in sports segment, a 300 /2.8 OS or a 400 /4 OS.
a 1,7x extender would be nice. A bit longer than the 1,4x but with better optics than the 2,0x? OR... a extender zoom. 1x - 2x or something. Would be cool but since nobody has done it yet it is probably not a good idea.