Disclaimer:
Apparently, B from Apprentice has suggested a similar format, I always had this format in my head since I made a format similar to it in 2016. It's a fairly standard format but worth mentioning here for some of the more detailed responses than you would get in Discord.

(It's a copypasta but you'll get the gist)

"You know what I'm thinking about doing
a Champions League Clan League
Even better, a Clan Champions League
Better sounding at least.
Get about 16 clans in (which is possible as 7 clans in A and B) and you get 2 good qualifiers clans.
Divide into groups of 4.
Top 2 advance to a single elimination of 8 clans.
Could bring in a Europa league for the 3rd finisher clans.
How would the games be done? Simply do it CL style. 6 1v1s 3 2v2s and 2 3v3s against the other clan... And base it out of 40 points.
Do it like football.. If it's 20-20 draw on points.. Give 1 point in the groups.
You would be playing the same amount of games as you would in Clan League but on a more cup format which increases the fun.
Substitutions can be done more fluidly as you can simply change for the next round."

Other stuff to add/clarify:
* You can do pre-qualifying rounds to help filter clans to good group sizes.

Any questions/feedback is welcomed. I'll try and be a beautiful poster boy for this idea.

Limiting CL to only 18 clan is not a good idea, as that would leave out a good chunk of clans that like to play

I think you could easily allow more clans by having qualifier matches.

Give say top 4 clans direct entry, then have 6 qualifying groups where the top 2 clans in each group qualify.

Or 8 direct entrants, and 8 groups with the winner of each group qualifying.

@Cowboy

You can be flexible with any number with how Huddyj describes it, you can mess around with the format to fit almost any number theoretically.

I really like it

I don't like it, sorry. You will have luck of the draw that way. Tournaments to determine champions only work when you have a regular season to seed teams

Why not use Clan League 11 to seed teams? Instead of a "Regular season".

Division A = top seeds.. then Division B next seeds.. and so on..

Surely using clan league 11 is nearly the perfect substitute for seeding instead of a "regular season"?