?bridges possibilitys ?

[emmanuel]

http://fileuniverse.com/images/bollocksbridge.JPG

is a land units can be under or on others ?(seed the walking factory work good but be a transport factory=scripting a mobile factory is makabl?)
is a bridge or a tower is a futur possibility?
is planes rebound or stop when paths cross?
i m novice about vtol units=is possibl to move a group of plane with diferent .fbi flightheight at same speed in a volumic wave (a cubic)?