It's as if SE considers 4 the minimum number to create a FC or buy a plot. You're the one that wants to change the requirements to maintaining at least 4 members at all times. I'm sure SE realises that a FC may lose a member before they grow and isn't looking be as over the top as you are, thankfully.
Why should the initial requirement and the maintenance requirement of member numbers be the same. Seems pointless to only buy a plot with a FC with 4 members if dropping 1 member means you all lose the house you worked towards. I'm genuinely fascinated you can't figure that out.