If you have many inputs scattered around various ports and you want to "gather them" in one consecutive block so you can iterate over them using a loop then sure, why not. Otherwise I must say I don't see the point of doing that. You might as well simply alias the bit variable directly to the port bit/pin and be done (after all, the Port registers is just another byte in memory - right).
Code:
Button4 VAR PortC.3
You'll save RAM, FLASH and processor cycles by not first copying the value of one bit variable (PortC.3) to another (Button4) only to then evaluate the state of Button4 variable.

But, I might be missing the point alltogether, in which case I apologise.

/Henrik,