This is NOT an attempt at self-promotion. The first Monster Island that I remember as a kid, was the one from the Godzilla movies made by Toho. Obviously you would have to parody them. I think that Garuda and M2-Wyvern might already be parodies of MechaGodzilla.

So in any case, the island always had lots of monsters, but one skill I would like to highlight is Godzilla's ability to heal or power up when he is electrocuted. That could either work as stamina regeneration or actual healing.