Odd UT/bonus ideas: certain buildings being constructed but not by villagers

• scouts can build outposts

• (UT) siege towers can transform into guard towers (can't transform back)

uses a "transform unit" in AGE, same as the treb

• walls can build walls and gates (for the tile next to them, at a slow rate).

I have a problem with the last one. Is it possible to make it so that when a unit is built it always tries to do a specific task (i.e. in this case: when a wall segment is built it automatically tries to complete any nearby wall segments).