Houserule: what if Warlocks could replace all invocations on level up?

[KorvinStarmast]

Still at a cost (potentially needed healing) and only 1 x per rest. Gradual evolution not instant change. Like you I wanted to give a little more flexibility without breaking the class.

I like this. Making invocations more flexible strikes me as value added, since clerics and wizards can change their spells overnight as well ...