Doable; an example follows. The values can be tweaked to taste, but what this does is make a 1,000kt unit that can be built, then sent into orbit, where it stays. The only thing it can carry is a single Space Yard component, and in combat it looks like a space station. I haven't tested it since the demo won't allow it, but it should work.
This goes into VehicleUnitTypes.txt (note the line maximum in space- this restricts the player from building a horde of these things):
<font class="small">Code:</font><hr /><pre>
Vehicle Unit Type Name := Space Yard
Unit Texture Start X := 0.50
Unit Texture Start Y := 0.50
Unit Texture End X := 1.00
Unit Texture End Y := 1.00
Maximum In Space Per Player Per Sector := 1
Number Of Unit Capabilities := 13
Unit Capability 1 Type := Can Communicate
Unit Capability 2 Type := Can Be Scrapped
Unit Capability 3 Type := Can Self-Destruct
Unit Capability 4 Type := Can Be Fired On And Destroyed By Owner
Unit Capability 5 Type := Can Be Launched Into Space
Unit Capability 6 Type := Has Spaceyard Capability
Unit Capability 7 Type := Has Facing
Unit Capability 8 Type := Can Obscure Sectors
Unit Capability 9 Type := Can Be Deconstructed And Analyzed
Unit Capability 10 Type := Can Be Transferred While In Cargo
Unit Capability 11 Type := Cannot Move And Tracks Target
Unit Capability 12 Type := Can Be Mothballed
Unit Capability 13 Type := Can Be UnMothballed
</pre><hr />
This goes into VehicleTypes.txt:
<font class="small">Code:</font><hr /><pre>
Name := Space Yard
Short Name := Space Yard
Description :=
Code := SY
Vehicle Type := Space Yard
Maximum Level := 10
Tonnage Space Formula := 1000
Tonnage Structure Formula := 1000
Cost Minerals Formula := 500
Cost Organics Formula := 125
Cost Radioactives Formula := 125
Engines Per Move := 0
Maximum Model Size := 20.0
Vehicle TopDown Picture Index := 10
Vehicle Portrait Primary := [%EmpireName%]_Portrait_Spacestation.bmp
Vehicle Portrait Alternate := [%EmpireName%]_Portrait_Spacestation.bmp
Vehicle Portrait Default := [%EmpireName%]_Portrait_Spacestation.bmp
Vehicle Large Portrait Primary := [%EmpireName%]_LargePortrait_Spacestation.jpg
Vehicle Large Portrait Alternate := [%EmpireName%]_LargePortrait_Spacestation.jpg
Vehicle Large Portrait Default := [%EmpireName%]_LargePortrait_Spacestation.jpg
Vehicle Inv Portrait Primary := [%EmpireName%]_InvPortrait_Spacestation.jpg
Vehicle Inv Portrait Alternate := [%EmpireName%]_InvPortrait_Spacestation.jpg
Vehicle Inv Portrait Default := [%EmpireName%]_InvPortrait_Spacestation.jpg
Vehicle Inv Configuration Layout Primary := [%EmpireName%] Spacestation Layout
Vehicle Inv Configuration Layout Alternate := [%EmpireName%] Spacestation Layout
Vehicle Inv Configuration Layout Default := [%EmpireName%] Spacestation Layout
Vehicle XFile Class Name Primary := [%EmpireName%] Spacestation
Vehicle XFile Class Name Alternate := [%EmpireName%] Spacestation
Vehicle XFile Class Name Default := [%EmpireName%] Spacestation
Vehicle Texture Start X := 0.25
Vehicle Texture Start Y := 0.75
Vehicle Texture End X := 0.50
Vehicle Texture End Y := 1.00
Space Combat Maximum Speed Per Movement Point := 0.0
Space Combat Turn Rate Base := 0.0008
Space Combat Turn Rate Decrease Per kT := 0.0000005
Space Combat Turn Rate Minimum := 0.0001
Space Combat Acceleration Rate Base := 0.0
Space Combat Acceleration Rate Decrease Per kT := 0.0
Space Combat Acceleration Rate Minimum := 0.0
Space Combat Deceleration Rate Base := 0.0
Space Combat Deceleration Rate Decrease Per kT := 0.0
Space Combat Deceleration Rate Minimum := 0.0
Space Combat Banks When Changing Height := FALSE
Ground Combat Maximum Speed Per Movement Point := 0.0
Ground Combat Turn Rate Base := 0.0
Ground Combat Turn Rate Decrease Per kT := 0.0
Ground Combat Turn Rate Minimum := 0.0
Ground Combat Acceleration Rate Base := 0.0
Ground Combat Acceleration Rate Decrease Per kT := 0.0
Ground Combat Acceleration Rate Minimum := 0.0
Ground Combat Deceleration Rate Base := 0.0
Ground Combat Deceleration Rate Decrease Per kT := 0.0
Ground Combat Deceleration Rate Minimum := 0.0
Ground Combat Banks When Changing Height := FALSE
Number Of Abilities := 2
Ability 1 Type := Combat To Hit Defense
Ability 1 Description := Large size makes base [%Amount1%]% easier to hit in combat.
Ability 1 Scope := Space Object
Ability 1 Range Formula := 0
Ability 1 Amount 1 Formula := -20 + ([%Level%] - 1)
Ability 1 Amount 2 Formula := 0
Ability 2 Type := Ship Maintenance Cost Modifier
Ability 2 Description := Reduced wear and tear allow for a decrease in maintenance cost of [%Amount1%]%.
Ability 2 Scope := Space Object
Ability 2 Range Formula := 0
Ability 2 Amount 1 Formula := -50
Ability 2 Amount 2 Formula := 0
Number Of Requirements := 2
Requirements Evaluation Availability := 1
Requirements Evaluation Allows Placement := 2
Requirements Evaluation Allows Usage := TRUE
Requirement 1 Description := Empire must have at least tech level 1 in Ship Base Construction.
Requirement 1 Formula := Get_Empire_Tech_Level("Base Construction") >= (1 + ([%Level%] - 1))
Requirement 2 Description := This vehicle cannot have any movement.
Requirement 2 Formula := Get_Design_Ability_Component_Count("Movement Standard") <= 0
</pre><hr />
And this goes into Components.txt:
<font class="small">Code:</font><hr /><pre>
Name := Space Yard
Description := Ship construction component which can work on one ship at a time.
Picture Number := 8
Maximum Level := 21
Tonnage Space Taken Formula := 400
Tonnage Structure Formula := 1000
Cost Minerals Formula := 200 + (([%Level%] - 1) * 2)
Cost Organics Formula := 0
Cost Radioactives Formula := 500 + (([%Level%] - 1) * 5)
Supply Amount Used Formula := 0
Ordnance Amount Used Formula := 0
Can Be Placed On Vehicle Types := Space Yard
Can Be Placed In Ship Sections := Inner Hull, Outer Hull
Component Type List := Technological
General Group := Construction
Custom Group := 0
Number Of Requirements := 1
Requirements Evaluation Availability := AND
Requirements Evaluation Allows Placement := TRUE
Requirements Evaluation Allows Usage := TRUE
Requirement 1 Description := Empire must have at least tech level 10 in Space Yards.
Requirement 1 Formula := Get_Empire_Tech_Level("Space Yards") >= (10 + ([%Level%] - 1))
Number Of Abilities := 6
Ability 1 Type := Space Yard
Ability 1 Description := Can construct with [%Amount2%] minerals per turn.
Ability 1 Scope := Space Object
Ability 1 Range Formula := 0
Ability 1 Amount 1 Formula := 1
Ability 1 Amount 2 Formula := 1000 + (([%Level%] - 1) * 100)
Ability 2 Type := Space Yard
Ability 2 Description := Can construct with [%Amount2%] organics per turn.
Ability 2 Scope := Space Object
Ability 2 Range Formula := 0
Ability 2 Amount 1 Formula := 2
Ability 2 Amount 2 Formula := 2000 + (([%Level%] - 1) * 100)
Ability 3 Type := Space Yard
Ability 3 Description := Can construct with [%Amount2%] radioactives per turn.
Ability 3 Scope := Space Object
Ability 3 Range Formula := 0
Ability 3 Amount 1 Formula := 3
Ability 3 Amount 2 Formula := 2000 + (([%Level%] - 1) * 100)
Ability 4 Type := Tonnage Repair Ship
Ability 4 Description := Can repair [%Amount1%]kT of ship tonnage per turn.
Ability 4 Scope := Space Object
Ability 4 Range Formula := 0
Ability 4 Amount 1 Formula := 200 + (([%Level%] - 1) * 20)
Ability 4 Amount 2 Formula := 0
Ability 5 Type := Tonnage Repair Unit
Ability 5 Description := Can repair [%Amount1%]kT of unit tonnage per turn.
Ability 5 Scope := Space Object
Ability 5 Range Formula := 0
Ability 5 Amount 1 Formula := 60 + (([%Level%] - 1) * 20)
Ability 5 Amount 2 Formula := 0
Ability 6 Type := Tonnage Repair Facility
Ability 6 Description := Can repair [%Amount1%]kT of facility tonnage per turn.
Ability 6 Scope := Space Object
Ability 6 Range Formula := 0
Ability 6 Amount 1 Formula := 150 + (([%Level%] - 1) * 20)
Ability 6 Amount 2 Formula := 0
Weapon Type := None
</pre><hr />