Research option for wall and GDI MG nest/Defense Scorpion

Of all units in both the defense and offense research tabs, only the wall and the first defensive unit is missing a upgrade in the research tab. The units does not even exist in the defense tab! I would suggest either a spiked wall upgrade or a instant repair upgrade for the wall. The spiked wall hurts any offensive unit that pushes against it, while the instant repair upgrade works like the anti-infantry/tank barriers. For the scorpion, it should be a laser cutter upgrade, or something similar to the defensive predator. The GDI MG nest should have the same upgrade as the Nod MG nest.