I swear someone has asked for this before, but give people to customize Issac how you can in the game, which characters that make it easier, and challange characters. And you can unlock them by using Issac points you get by going beating a chapter (Also make sure prevent people from quitting the game when they're close to death and have everything restart, instead have it work like Pvz 1 and 2 so people can't cheat and when you continue an unbeaten level ur in the middle of it starts with all enemies exactly where they were).
Idea: Blue Baby ("..." In game)
Reuire: Beat a whole chapter without using any baby over 3 hearts once.
Cost: 10 Issac points
Type: Challange
Challange: You can only have a max of 3 hearts, but every 5 enemies killed gives a half soul heart (max soul heart count is 7) that works like how it does in the og game; it's used up when you spend it on a baby and dissapears when used fully. All babies also have 20% less damage, but all levels have less enemies by 20%.