I would like to be able to change my target while I am casting my spells/abilities/actions and have the action execute on the new target instead of being interrupted.

Especially for magic ranged DPS classes, I find it annoying that I spend 3 seconds to cast a skill, my target dies or otherwise becomes invalid before it executes, my casting gets interrupted, and now I have to start the casting all over again for a new target.

Would it be a bad idea to add a second target check to the end of the cast timer and have the skill execute on the second target instead? I know in most high end raids there is only one target, the boss, but his could help combat fluidity for the normal dungeons by rewarding casters for mechanical skill ie. paying attention and switching targets before cast timer completes.