World club cup knockout

What is the maximum teams you can have in a cup tournament when running a usual league with all domestic cups as well

Basically I would like a usual season but a new knockout tournament featuring every winner from every league in the , or even featuring every team in all the top level leagues in the world - the games would be one off random draw like FA cup.

Also, I would like to extend the FA cup to include all teams from English, Scottish, Welsh, Northern Ireland and also Ireland