You can do that anyway with the wait command. But I'm not referring to the wait command, I'm just referring to ability queuing before the GCD ends.

I'm more concerned about the loss of fluidity when using macros. In my example about, using Blizz III, Thunder II, and Fire III back to back to back feels very fluid and the timing is perfect. But, insert a macro for Thunder III/II/I and now you end up having to hammer the macro instead of the rotation having any kind of flow to it. It turns a very useful macro into a headache a lot of the time.