It makes sense that LF could have gotten hold of
Gendry but Im not sure how that benefits the Tyrells.
The Lannister legitimacy to the throne will definitely be
challenged especially since Cersei's incestuous ways are
coming to light and Im sure Lancil knows about Cersei's
bastard children.

But how does that get the Tyrells free? That appears
to me to be Lady Olennas main goal. Olenna doesnt seem
so petty as to get some payback on Cersei but forget about
her grandkids locked up.

If Tommen is proven illegitimate does that rescind prior
decrees from the throne, like arming the Faith?
Thats the only way I see Margorie and nem gettin free,
right now at least.