That's an interesting proposition. Whilst I loved Sadler's performance as Sloan, Malcolm McDowell would have taken it to another level. His performance as Soran in 'Generations' was flawless. Seeing McDowell and Siddig bouncing off one another would have been mesmerising.
McDowell did a descent job in "Generations" considering that, according to his nephew, one Alexander Siddig, he thought the script was "shit."