Colin Clive has no living relatives that are known. Its uncertain as to whom to contact concerning the use of his likeness. So, in lieu of releasing a product and getting sued later for not getting consent, SSC simply declines to make a Dr. F. Sad but true from what I hear.
Well I say make one, and see who pops up to sue! That would either clear up who has the likeness rights, or if nobody sues, Sideshow has no problem anyway.
But with the likenesses of the dios recently, they wouldn't need Clives likeness