I think small metroidvanias allows Jani to try different things (map/enemies/magic/shops) which is good, and in big metroidvania he will have to choose what to use for whole game (you can't change game's main idea mid-game, right?)
i know. i love mini-vanias. But I would love to play a scaled up version, plus it would be available to a wider audience AND compensate him better for his work