For sure that a tournament like this would need some seasons to be completed.

It could work with invitations to join the next stage i you qualified.

We need it to be in equal conditions, so a IC redesign which have a "standard" training system may be the best option.
Teams would keep the progress without losing the 20% so at some point, after some seasons of tournament the situation would remain quite fair.

We could have some seasons where to have like, 2 playoffs rounds each week and then some seasons where to play some kind of group stage.

It could too be limited, based on a particular seasonal performance or a event + achievement won that could give a ticket to join that tournament.