Raimey,
I have played around with adding rims to rimless cases and actually made some rimmed cases that way. You need to have a hydraulic press that is powerful enough to swage he material onto the prepared donor case. You also need to have a lathe to make the dies you need, prepare the brass material being added, and to shape/size the added rim. The brass rim material had to be annealed as soft as possible so it will flow, under pressure. If radical case forming will be required, you should do that before adding the rim to prevent damaging it during the sizing operations. The best way to make cases now would be to form them from 30 Blazer donor cases. Forming the cases would be easier than adding a rim and would likely result in better cases anyway. Since I got some cases with my rifle, I didn't have to do that much to be able to shoot it. I did experiment with converting 8x56R blanks that had a substitute for the bullet formed from the case so were long enough. Because of severe work hardening where they were crimped, I was unable to prevent cracking of the neck. I couldn't anneal the necks first because they were loaded and the cracks started while opening them up to remove the powder. I didn't have an 8x56R to fire the blanks in so I don't if starting with fired cases would have helped. Yoy seem to have pretty good supply sources, so I believe your best bet is the 30 Blazer for 5.6x61R cases. BTW My rifle is a "Remo" made by Rempt and I don't know of a connection to Chr.Funk.
Mike