Va is the maximum speed at which maximum load factor can be imparted w/o structural damage or failure. If care is taken aerobatic maneuvers can be done above Va but the limit load could be readily exceeded, if not careful, as the available load factor due to the high lift coefficients achievable at higher speed and the G -meter must be respected....
You have less and less structural margin for maneuvering loads as Vne is approached. Va is the speed at which if an airplane is stalled no more than a limit load will result; since maximum loading on the wings occurs at the stall.
Va does not protect against rapid control reversals and no aerobatic maneuver requires such control inputs anyway ...
even if you wanted to say reverse a snap roll it would require momentary centering of the control surfaces before going the other way i.e complete unloading first otherwise a resonance condition maybe set up which can destroy the structure very rapidly
of course in the above case you'd be forced to wait to get up a new head of steam anyway...which is good!