Is not as simple as it looks, this is about clubs so is hard to create a World CUP, you will need something like new servers is almost like creating a new copy of the game just for that.

Regarding the regional cup, this is also super complicated because some people will look to go on another regions with a lower number of players to take the advantage.

but UEFA CUP / EUROPA LEAGUE is something I always supported and it will be cool for those who can't get in Top 4 especially now when is super hard with the new draw system.