Has anyone set up there YZ with WR timing to soften the hit??
That has to be done by actually changing the camshaft on the '03 and later auto decompression models, because to change the cam timing also changes the timing of the decompression phase. Going from WR to YZ causes the bike to have too little compression to start reliably, if at all, and going from YZ to WR effectively disables the system, making the bike nearly impossible to turn over. Some power seeking WR owners have ground the decomp pin, but taking such "bush" measures with an internal engine component is, frankly, barbaric, and I don't advise it.
But, yes, some YZ450 owners have installed WR cams and some of them did like it better, but if you want to soften the bike's temperament, and make it more fun and easier to live with, the flywheel is the way to go.