Two things...
1) I'm not entirely opposed to virtual kickbacks, especially on Pro models. I sort of like how it safely shoots the ball back into play, especially on shooter lanes that go to the rear orbit.
2) Kickbacks typically involve having a curved rail over the outlane to direct the ball back into play. This would require new games to consider this requirement and can partly change or limit playfield geometries and inlane/outlane setups. Not a big issue, but something to consider.