The research on this is quite solid. Incline running only improves speed if kept to a grade of 3% or lower, performed on a natural running surface. Anything else alters mechanics to such an extent that there is no longer transfer to natural sprinting. Specifically, it is too quad dominant and the ground contact times are way, way too long. It does nothing for a player's speed when his sprint training involves .5 second foot contacts, but during level sprinting his foot is only on the ground for .1 seconds. The player simply isnt in contact with the ground long enough to produce the higher forces he developed during training. And he is also trying to produce those forces with a different motor recruitment pattern.
I also think Oly lifts for football suck.
I thing strongman has some applicability, provided it isnt perfomed in the lactic zone. But Id be surprised if it isnt.
And there is what I haven't seen done, namely the development of reactive strength or alactic conditioning.