I'm trying to increase the number of Extra Attacks granted at higher levels as a feat or as a subclass feature, like Fighters get as a base class feature. What do I need to do to make this show up on a character sheet properly? I'm using Ryoko's and want to give one of my players the Fighter version of Improved Extra Attack from that book, but I can't replace the Extra Attack base class feature, and don't know how to replicate Fighter's base class features Two Extra Attacks and Three Extra Attacks, in order to make the Improved Extra Attack for a different class.