First,I'm not doing the research to tell you if the case dimensions are compatible to make the cases in question from 30-30,or if its a good or safe idea.
I just don't know.This isn't a recommendation,I'm just answering part of yur question.
However,in regard to going from the rimmed 30-30 case to a rimless cartridge with an extractor groove...that can be done on a lathe.
The rim would be turned off and the groove would be cut with a tool ground to the desired form.
If this is done,care must be taken that there is enough brass thickness in the 30-30 so the brass is as strong as the factory brass you are trying to replicate.
Strength is very critical in the case head area. Thin sections can hurt you.
Ihave no clue about "adding a ring....". Does not sound right.