I changed the scenario a bit today and thought about similar situation but really I guess no different.
I was thinking about a bolt circle pattern around this 3/4 radial hole. How in the world would I be able to approach that with out a Y-axis. Sure I can move over on Z axis but how would I move up or down from that 3/4 hole without moving the C-axis.
This is why I think I anwsered my own question... just had to think tad more I guess. Bummer for me I guess.