That depends if you can define multiple "cases" with forbid (as with the example of the requirements of the "study" facility in Piratez extended).
Also important, it depends if a building under construction already gives its trait for such case (forbidding), otherwise you have a hole in the method.
As pointed out by Solarius, if you give facilities a trait of "unique" and at the same time they forbid themselves if the trait "unique" already is given by another facility in the base, you have a unique facility. If some facilities share the same approach, then is a "choose one facility".
BUT (big but), if you also start branding other facilities with a common trait (let's say, branchA) and you forbid them with another one (branchB), you can segregate "families" of facilities, forcing the specialization.
in such conditions you could define "common", "branchA", "branchB".
in terms of game mechanics, you could recycle the system in each branch to your will, isolating their behavior with the rest of the game.
As this last statement is kind of gray I put the idea I've been going around theses days.
"Casino Base".
One unique barrack with space for X people, Y storage and Z work spaces. Branded "unique" and "BranchB". (business HQ). It is the start of the branch and that inmediately forbids "BranchA".
Everything that does go with the flow and breaks the mechanics go branded "branchA", including workshops, quarters and stores.
- Storage becomes dedicated to storing a merchandise or HWP called "Criminal roller" (not transferable). Each give and income but occupies 1 point of storage. Dedicated facilities gives more storage (accommodations).
- Manufacturing becomes specialized, it creates this "merchandise" or transforms other materials. I can use the quantity of "merchandise" to set a minimum value in order to be able to do other stuff. Additional facilities give more manufacturing options, all of them under margins of "control" thanks on the limitation on workshop space (the cash cow can't skyrocket unexpectedly). Additional facilities gives additional manufacturing projects (taverns, variety shows, safe depots, racing garage, parking slot, underground arena, Supervillain comms room,etc). You can tier them, you can bind them by research or by requiring another room trait (sky is the limit).
- Living space becomes a tradeoff, If the base is under attack you need soldiers but the quantity and their equipment impacts on the revenue given by the "merchandise" and the runts working in the projects. Having the merchandise going around during assaults (if HWP) could go directly into a monetary and score loss.
Sickly conceived, yes, I know. But this opens a lot of gameplay options for everyone to conceive
