I vaguely seem to remember being able to build a Relay bunker and Gun towers on the hills beside the base in River 4 with the 1.2 engine. I'm not sure thats possible any longer.
Not certain, only tried once.
I thought Builders had their crampons back?
Crampons? You mean climbing hills? They can do it to some extent, but not fully as in 1.2 as far as I can see. If they get stuck (sliding in one place), I just knock them up (bad wording :D ) or use sonic wave, etc.
they usually build thru the walls if it isnt that high, and i have seen tons of spirs on top in a 1.3 game, but that could be sonic, maybe a tug...