Hi,
I don't see any issue in defining as V7 as i check V7 is not defined in the system.
So can define it as V7. I am using R1,R2 and Z1 in my system as repository name. I think till repository name is not being used in OAC0 you can use it.
Just found one note .
315604 - Repositories A2,A3,A7,D1,D3,DT,F1,F2,I1,IR
The above note does not tell you about the naming convention but tell you actually which all repository are there and came from the sap system as customising .
Thanks
Rishi Abrol