What Jeff is describing is the classic Ford McPherson strut suspension, which (for economy and simplicity) reduced the number of parts and unibody attachment points to an absolute minimum. The Ford Fiesta shared that design, which as noted uses the sway bar for fore-aft suspension control. (I used to own a street TR8 and a street Fiesta, never really looked at the front suspension on the TR8 but did on the Fiesta.)
Speaking of the Fiesta, it used a typical small diameter shallow U shaped sway bar which did a poor job of fore aft control. At one point my Fiesta developed a significant sideways pull - which a savvy body/frame/alignment guy "fixed" by using a hose clamp to bias the sway bay to one side at the frame mount bushing. Clever fix (it worked) but shows the flimsiness of the design.
I'm not looking at the Prod rules right now but I'm sure that sway bar (ARB) is free but suspension type and attachment points are fixed, Not sure how all of that interacts when the sway bar is also a suspension arm.
My GUESS without poring over the rules (dangerous of course) would be that you absolutely can reinforce the ARB and its mounting to stiffen things, if that's a goal. Not sure if you can:
A) add a second ARB, adjustable or not.
B) sever the existing ARB, at which point it's not an ARB anymore
I'm sure that you COULD modify the existing ARB in such a way that it could be garage adjustable if not cockpit adjustable wrt ARB stiffness.
^ I think that this comment is useful food for thought but hardly a definitive answer