All that is required is the capacity to strike deep enough into Russia to hammer Russian artillery and missile sites that are sitting beyond the Russian border and lobbing shells, rockets and missiles into Ukraine. Russia has been able to create a buffer zone in the Kharkiv region by firing from their side of the border. This change of posture from the West will help eliminate that buffer zone advantage that Russia currently enjoys.
It will also allow Ukraine to fire air defense missiles from systems such as Patriot, into Russian airspace to challenge the SU-34s lobbing glidebombs from the front line.