If the flow allows "dog-bone" FETs then you can get
a W less than the (contact + AA oversize of contact)
that an ortho FET would require. What is min AA width?
You won't get below that in any case.
Wmin is usually lithography, Wmax (M aside) may
be either tap rules or the modeling guys saying
"can we quit now?" re the geometry-space they
have to cover.