Qian is a good idea. but changing Cash into Qian might not be one. Why not just launch a new Qian Coin? you can use the same algo as Cash if you like.
That makes absolutely no sense unless you're talking about doing a coin swap which is messy and generally a bad idea. Changing the name and doing a relaunch is a good idea and it has been done plenty of times as long as it's a better name which the community agrees on.