Instead of having different wall models as distinct build options, consider having just basic wall types and then features that can be built into them. Example:
Build the metal wall and have the basic solid panel. Then once constructed open up the build menu and open the "modifiers" section that displays the following options:
- Conveyor Bracket (aka; Perpendicular Conveyor)
- Conveyor Window
- Power Port (allows power to travel along the wall and to the other side)
This would actually condense down the build menu and make it easier to set up walls with layouts exactly like people want. You could build in a door on the right side with two conveyor ports in the middle and left slot. Conveyor Brackets could be positioned to allow belts to bend around corners more effectively by placing the brackets off-center. Certain features could also be made to exclude the addition of other certain features (Adding on an Archway makes multiple connection points inaccessible, for example).
Also consider spinning out this method of "modifiers" to include vehicles. You build a basic chassis and then add on upgrade features (harvester attachment to the front of the tractor and at the cost of speed and fuel consumption chop down and store plants that collide with the front of the tractor, like a vehicular chainsaw)