I'd like to see a few more of the main cast members of the '86 movie, as well as some classic G1 characters.
Movie set #2
Kup
Wreck-Gar
Cyclonus
Scourge
Classic G1 series #4
Ironhide
Wheeljack
Skywarp
Reflector
Something like that would reenergize the line, I'd hope. Maybe another set of flat-colored, cartoon re-dos would help too.
Oh! and a Unicron Vinimate!