Is this possible?

[Q]

Wow, thank you very much Fyron. This was exactly what I needed. As far as I see it will be the easier solution as I want to modify the basic and tachyon sensors. So there will be effectivly only one sensor allowed: either a long range but low sight level basic sensor or a low range but high sight level tachyon sensor.
Anyway you reply covered every possibility.
Really not bad for 4am!

[Q]

Well I found even a more elegant solution:
Instead of going to each vehicle I changed the component itself according to your suggestion Fyron:

Name := Basic Sensors
Description := Basic sensor package which allows detection of ships and space bodies at range.
Picture Number := 28
Maximum Level := 21
Tonnage Space Taken Formula := 10
Tonnage Structure Formula := 10 + (([%Level%] - 1) * 10)
Cost Minerals Formula := 200 + (([%Level%] - 1) * 2)
Cost Organics Formula := 0
Cost Radioactives Formula := 50 + (([%Level%] - 1) * 1)
Supply Amount Used Formula := 0
Ordnance Amount Used Formula := 0
Can Be Placed On Vehicle Types := Ship, Base, Satellite, Drone
Can Be Placed In Ship Sections := Inner Hull, Outer Hull
Component Type List := Technological
General Group := Sensors
Custom Group := 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 Sensors.
Requirement 1 Formula := Get_Empire_Tech_Level("Sensors") >= (1 + ([%Level%] - 1))
Requirement 2 Description := Ship cannot have both basic and tachyon sensors.
Requirement 2 Formula := Get_Design_Ability_Total("Sight Level", 1) <= 1
Number Of Abilities := 2
Ability 1 Type := Sight Level
Ability 1 Description := Allows scanning at level [%Amount1%].
Ability 1 Scope := Space Object
Ability 1 Range Formula := 0
Ability 1 Amount 1 Formula := 1 + ([%Level%] / 5)
Ability 1 Amount 2 Formula := 0
Ability 2 Type := Sight Range
Ability 2 Description := Allows scanning out to a range of [%Amount1%] sectors.
Ability 2 Scope := Space Object
Ability 2 Range Formula := 0
Ability 2 Amount 1 Formula := 3 + (([%Level%] - 1) * 1)
Ability 2 Amount 2 Formula := 0
Weapon Type := None

and

Name := Tachyon Sensors
Description := Modulating tachyon sensor grid which can detect cloaked ships in a system.
Picture Number := 36
Maximum Level := 26
Tonnage Space Taken Formula := 40
Tonnage Structure Formula := 40 + (([%Level%] - 1) * 10)
Cost Minerals Formula := 1500 + (([%Level%] - 1) * 15)
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 := Ship, Base, Satellite, Drone
Can Be Placed In Ship Sections := Inner Hull, Outer Hull
Component Type List := Technological
General Group := Sensors
Custom Group := 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 4 in Sensors.
Requirement 1 Formula := Get_Empire_Tech_Level("Sensors") >= (4 + ([%Level%] - 1))
Requirement 2 Description := Ship cannot have both basic and tachyon sensors.
Requirement 2 Formula := Get_Design_Ability_Total("Sight Level", 1) <= 1
Number Of Abilities := 2
Ability 1 Type := Sight Level
Ability 1 Description := Allows scanning at level [%Amount1%].
Ability 1 Scope := Space Object
Ability 1 Range Formula := 0
Ability 1 Amount 1 Formula := 2 + (([%Level%] - 1) * 1)
Ability 1 Amount 2 Formula := 0
Ability 2 Type := Sight Range
Ability 2 Description := Allows scanning out to a range of [%Amount1%] sectors.
Ability 2 Scope := Space Object
Ability 2 Range Formula := 0
Ability 2 Amount 1 Formula := 1
Ability 2 Amount 2 Formula := 0
Weapon Type := None

And it seems to work. As soon as you added one sensor to your design you cannot place a second sensor anymore in the design.

[Fyron]

Really? I thought that the design component and ability count functions didn't work when used in component requirement fields. Hmm... wonder if Aaron changed something recently and didn't tell us. Awesome.

That method has a slight drawback, in that if a player doesn't know about the mutual exclusivity, and doesn't pay too close attention to the reqs list in the component descriptions, they won't know what is going on when they try to add the second component. This might not matter so much, but is worth consideration.