So to sum up what I am the post am saying. Encourage intelligent players to try new things as you wanted. Encourage ingenuity. Do not use invisible wall type methods to close players off from areas and places they can clearly reach. If players through intelligent choice find a way to kill the boss legit but in a way that makes it to easy find a way to make that strategy less plausible thus encouraging players to not do it but still allowing them too even if it will likely fail due to the new mechanic. It's about fixing things in a way that feels legit and makes sense and doesn't steal from the experience and the ingenuity