I would like, as controller mapping options, the options to null directions and inputs. Meaning that using one would allow the c-stick to input only directions for one frame by nulling an attack input with another button. Would also allow things like buttons that have multiple purposes depending on what input you null. I believe somewhere PMBR said that this isn't currently possible though, so I'm not holding my breath.
What I think PMBR SHOULD go for is buttons for individual things, like a nair/neutral attack button, as well as a true attack stick with analog functionality, meaning a c-stick that does both attacks and tilts.