the teleporter is a good one i recon, there was one in one of C&Cs tho IIRC it was quite limited in some aspect which made it kinda a luxury more than a useful weapon.
OMG ! This was called Chronosphere, and was not a luxury, but one of the most powerful weapon in game ! And it in C&C Redalert and C&C Redalert2. You can't even imagine what was able to be done with this nice piece of technology.
Back to subject, i love terraforming ideas. You can already do that with mines, but this is not the easiest way. And for bridge building, you can use a con, they can 'restore' map, and so make bridges on trenches.
What we need is a unit which is specialized in map modification. Low speed, can climb hard slopes, can make the terrain go up and down. This can be seen as a new building in the unit construction menu : high ground (build a square step) or low ground (remove a square step).
Or else, i will stick to mines terraforming
I also like the idea of the twin factory, and also the peewee canon. Should work like a transporter. You put a unit in it, and than make it shoot. it use the unit as a projectile, have low accury, high range. You can so make any unit land somewhere on the map. The unit should take dmgs from the impact. But just imagine a flying Krog landing in enemy base, on impact, he lose half his hp, but destroy any building he go in

And of course, flying units are repulsed by the new SJ repulsor
