Finding the right League System for the SBL

I'm in the process of designing the league page, the page functionality and the league system.

For the system I'm not sure what to do and I'm starting with this suggestion and I'm looking forward to your feedback.

The goal is to have a league system that can carry a very big amount of teams, in case Supraball becomes ultra successful. So I made the league amount double on every step downwards.
The goal is also, that a good team can rather quickly get promoted from League 5 to League 2 in a reasonable time if it is that good. So the leagues are small and seasons don't take too long.

What do you think? What could be a problem, what could be better? Or do you like it as it is?