Except that Mifune does not play a reluctant hero - he's her general, it's his duty. (he's a lot more like Obi Wan in this sense)
(you could argue that the basic storyline is more based on the searchers!)
anyway, the basic storyline ain't exactly original full stop.
I wouldn't go anywhere near as far as that - inspired yes, but remake, no way. Star Wars was a homage to many films.
The main "lift" from Hidden Fortress is of the two main peasant characters - basically C3PO and R2D2.
Oh, and OUATITW.