Very nice post. I agree with some stuff and would probably agree with everything if we weren't talking about ZU/ZUPL, which in my perception you might be misunderstanding the intentions of this change and lacking some information about how our tournaments usually go.
To preface, you mention a lot of your experiences with Monotype and PU, which are valid to bring across the board but mostly as addendums imo. I get that you speak in a tone more of separating officials (SCL/SPL) to non officials / subforum stuff, but I don't think that's a very precise way of elaborating on this. There is a very large gap in interest numbers between UUPL and PUPL for example, and so there is one between PUPL and ZUPL or MPL and ZUPL.
Now I'll be answering your arguments individually.
Yeah thinking only on the number of people playing per week, that would be correct. The second part though? ZUPL is supposed to be the most prestigious and of highest level ZU team tournament, and unlike other metagame PLs, it does not work simultaneously as a stair for officials. I can relate: I was the tournament's overall MVP last year and that isn't really something you can use to get into officials like you possibly could in some other metagame PL. Yes, I was playing an oldgen, but let's not larp like a good ZUPL SV record would put someone in SCL. Therefore, this seems like a non issue for me.
I really don't think this is true.
When I asked people to name names on snubs for last ZUCL, in which they were complaining 8 slots created some:
View attachment 840478
Spoiler: he did not name names
Meth Master, a regular, then answered me talking about himself (fair) and Praise the Salt (I don't really know much or see this guy in tournaments a lot but he's a regular). I actually had Meth Master as a sub in my plans but in VC during the auction people were asking for other people and yeah you know how it goes. I thought someone else would for sure pick them up, though. Note that ZUCL was a 8 teams tour but with 8 slots. IMO it was very superior to ZUPL hard in game quality terms, so I do not think the quality talk is entirely fake, and the few snubs people could even name were more results of bad managers drafting rather than anything else.
tl;dr: snubs are produced by people drafting badly, not by not having enough spots, and I can really only affirm on methmaster of these two.
As for tour players getting drafted again even if they flop: Not sure either, I guess it all depends on how much they cared and their results site wide from an year to another. I'd be happy to draft again some who played for me and didn't have a great record because they were getting themselves decently involved and trying to win for the team, but I also wouldn't touch again others who seemed they couldn't care less.
This is impossible when you barely get eight teams and still want to do eight teams. There is no way to filter whatsoever. ZUPL usually gets like 9-10 but like of these usually 3-4 feel either very very novice, or tour players who have quite literally never interacted within the tier and don't have notable success as managers elsewhere. You need to reduce the numbers of spots for a pickier filtering to happen.
I'm far from being the only one here. I get that you're speaking in general and not about me at all but if you search for "6x10" "5 weeks" or "6 teams",in the ZU discord, or if you just ask them, you'll see a lot of people in favor, a lot of which are some of the best managers or pool mainstays. In fact, I made it clear that I'm playing regardless of this
View attachment 840474
As a disclaimer so people don't think I'm nitpicking: I have no answer to the lineup adjustments thing you can do with 8 teams, I think those are still very possible with 6 (not sure if you would remember about Olympiad 3, in which Michael Jordan started as a sub for our team but started playing in week 3 to the playoffs iirc.) But yeah like you can obviously be more patient if it's 8 teams. For the playoffs race, yes eight teams has the potential to be more fun, but for ZUPL I don't really see a difference when, as I already stated, you often have two teams out by the end of week 5 or week 6. So week 7 is in practice with the same stakes of a week 5 of a 6-team tour.
Ultimately, I appreciate you coming here to post your opinion and perspectives. Seems more about you thinking the cons of six teams outweight the pros and I see it as the opposite, which is fair and we can agree to disagree.