My suggestion is to create a trait skill that makes movement skills break immobilize when you have a main hand dagger equipped. The actual skill could only work for main hand dagger abilities or both main and offhand. It would probably be more balanced if it only worked for main hand dagger abilities (burning speed and magnetic grasp) as ride the lightning is already an incredibly powerful escape mechanism.
I think the easiest way to implement this would be to add it to the windborne dagger arcana skill.