FB format.
If we continue to use the cup system, then we could even merge OFB and FB into one tournament: group stage - OFB, a certain number of participants advance from the groups, the finalists of the previous FB join them, and then it's Full Double Elimination.
and, moreover, only the player who took 1st place (!) advances to the next FB, everyone else qualifies from scratch. And there won't be any overlaps where players from the current FB cannot participate in the qualifiers.
Hold it once a year or less.
And also, perhaps we should introduce restrictions for signing up for the tournament, since this will still be the main tournament on HeroesWorld, so only already known players, players who have already participated in tournaments, and active newcomers should be allowed to sign up for the group stage.
PS: I ask for comments on this point.
Once a year might be too little; perhaps we should first hold the first combined tournament, see how long it lasts and with what interest it will go, and then, closer to autumn, assess the situation to see if there is a desire to play a second FB in the year.
Oh yes, and to add a twist to the tournament, also with Allrandom (honestly, the same pairs are already getting boring)