The premix thru the injectors is not the problem... (the turbo guys are running it)....
AND I do agree with Marv1 in that the fuel curve would need to be modified... with a control box like boondocker, Attitude or Power Commander.
The lubrication of the crank bearings would be the issue here.
The turbo guys have had decent luck with this but for non turbo sleds... IMO (as well as Indy Dan) you would have to modify the case and bearings to work with this layout.
The 600 IQR's (not the RR's) run premix, BUT... they have a sealed, greased bearing on the PTO side that needs replacement every 1000 miles or so. They also inject oil into the center gear cavity every race weekend.
You will have to be very carefull when mixing... preferably in a can where you can figure out the exact Ratio!
It can be done for sure... but it would require some engine mods to have a reliable setup.