As a solution for the Multitile Depot issue, and for complex station layouts, we could have a new object defining a customizable size grid (e.g. 3*4). Every tile in the grid points to an object in the existing pak and one is arbitrarily considered the "target tile" where to start building on click.
if all objects in the grid (except for "-") can be built (in 4 rotations), they are all built simultaneously.
e.g.
Name=DepotCluster
Dims=3,4
Target=1,0
Cluster[0,0]=Depot_Extn
Cluster[0,1]=Depot_Extn
Cluster[0,2]=Depot_Extn
Cluster[0,3]=Depot_Extn_Front
Cluster[1,0]=Depot_2
Cluster[1,1]=Depot_Station
Cluster[1,2]=Depot_Station
Cluster[1,3]=Depot_Station_Front
Cluster[2,0]=Depot_Extn
Cluster[2,1]=Depot_Extn
Cluster[2,2]=Depot_Extn
Cluster[2,3]=Depot_Extn_Front
(the inside objects could also be hidden not setting an icon)
Or
Name=ComplexTwoWayStation
Dims=3,6
Target=1,0
Cluster[0,0]=Station_2
Cluster[0,1]=Station_2
Cluster[0,2]=Station_2_Overp****
Cluster[0,3]=Station_2_Kiosk
Cluster[0,4]=Station_2
Cluster[0,5]=Station_2_Sign
Cluster[1,0]=Station_2_Sign
Cluster[1,1]=Station_2
Cluster[1,2]=Station_2_Overp****
Cluster[1,3]=Station_2
Cluster[1,4]=Station_2_Kiosk
Cluster[1,5]=Station_2
Cluster[2,0]=-
Cluster[2,1]=-
Cluster[2,2]=Station_Bldg_left
Cluster[2,3]=Station_Bldg_right
Cluster[0,4]=-
Cluster[0,5]=-