Sorry I'm not sure if this is possible to make, but can anyone make a WTF mod that gives heroes no mana cost on spells and no cooldown?
If this is possible, can it also be made multiplayer with others who have the mod?
This is not possible, as there is no multiplayer custom/practice mode.
You cant make multiplayer mods yet.
Wait untill the game is released and you will see all kinds of mods coming out.