A strong head voice? mmm hate those terms.
Sorry i think unless you can tilt and produce cry quality up to the Gs and the one B flat then there aint much point doing Tony. Its a legit sound and without that (or relying on what you call "head voice" would make Tony even more of a wimp than he is)
As for Marius some who have played the part in West End have sang it in higher keys. It just depends really. Michael Ball is certainly no "tenor" he is a high baritone. As is the current Marius, Hayden Tee. Great top notes but tons of depth down on the bottom. In fact he has a stronger lower range than the current West End Javert!
