Dunno if this has ever been brought up... but what about a teleporter structure (similar in form to the armory on the nf side) that lets you move between them.... fairly cheap, 100-400 res, can only teleport infantery, should take a long time to build (2-3 full engineerammo with repairupgrade), research needed before being placeable and only two of them can ever be placed by each side (if one is destroyed or recycled you can place a new one).
