Lelouch wanting to fight using his other strength instead of a skill given to him by other could manifest in him having super strength/speed or things like that. Or he could gain an ability like super eidetic memory (he reads a book on how to study kung fu/watches Suzaku training and suddenly becomes a kung fu master). IDK I'm just throwing out first thoughts.
And no it wouldn't be invalid! Just have a good explanation. Example: When Bruce Bannon hulks out, it's because he loses his temper and gains speed, crazy strength, and becomes really aggressive. All of those could be considered side effects?