That is not a great idea, you are just tier locking it to a certain tier with no rhyme or reason (feels like on of the bandaid patchs Calamity does to vanilla content, if I am being honest). This is worse, since ectoplasm is post Plantera, the same time you get access to Soaring Insignia, which invalidates TSpark when used with wings. TSpark's obtainability early on if you are willing to grind for them makes them fairly unique. If you really want it to be tier locked, something like post Skeletron makes more sense, since most people go to the Underworld at that time.