In retrospect, I find myself thinking that it would have been better for the Federation President in TUC to be another species; Efrosians do look more similar to Klingons than would be preferable if you're making a major motion picture aimed at a mainstream, non-Trekkie audience base.
It never occurred to me that Efrosians resembled Klingons until I came across this thread. It's only a slight resemblance at best, IMO -- It only goes as far as "long hair, bumpy forehead," a description that could apply to any number of Trek aliens.
And the Efrosians
really don't look much like the STVI version of Klingons, who, generally speaking, didn't have the huge hair that the Klingons in TNG and the other movies did.
Chancellor Gorkon's hair was pinned back,
General Chang was bald with a tiny ponytail in the back, Chang's daughter
Azetbur had a skullcap, the
commandant of the prison camp on Rura Penthe was largely bald with some stringy hair, and Brigadier Kerla and
Col. Worf both had straight hair that was tied up. Pretty much
every Klingon you see in STVI had long, straight hair that was kept flush to the side or tied back in a pony tail. Even
the Klingon Ambassador played by John Schuck had his hair pinned back, and he was probably re-using
the same wig he wore in STIV. Now compare all of those with
the huge wig that the UFP President had. There's just not that much resemblance.
The chances of casual fans being confused was pretty limited. It's only
because you're more of a hardcore Trek fan that you're even making this association.