Path Of

Well let's breakdown the very concept of imagination. Imagination is a thought conjured by our brain using creativity and desire which needs energy to fire up those neurons in our brains. Energy is something that cannot be destroyed not created but it is used to channel through things and it does change its form. A body with toon force i.e. Luffy unlocked, doesn't mean he has the ability to understand the usage of this energy in absolution. Because if he were to do so, his tiredness wouldn't exist and we wouldn't have seen Luffy getting old as a pushback from the ability. Maybe that is why Mother flame exists separately in the realm of One Piece.

Adding further to the concept of Nika himself, a god that brings smiles onto the people could very well mean him sharing his fantasy as Eiichiro-Kun stated. Now what that could be is an absolute mystery XD. Conjuring objects from another reality does require energy and what goes into the mind of Nika is something so funny that makes even heavy hitters like Gol.D.Roger and his entire crew fall in love with him.

To have absolute power one must know that it does attract absolute corruption. And to know that value of both creation and destruction, is where the balance of eternal existence lies. Maybe that is why in our reality everything has an expiry date and we experience time in a linear way. Imagine how the imagination of a being look like where time is constant and energy is just converted without any loss.