Regarding this idea:
If all members are allowed to fight,
Most of them should fight. The more the better for a guild. The question is how many top scores should be counted 
27 seems like a good number. We have less than that fighting in our guild as it is not required, but a 90% participation/10% buffer for absences seems to strike a good balance for me while not stepping on the toes of the “competitive” too much. I’m sure some will not like the idea, but I really don’t see the harm in giving some breathing room for real life. If anything, this makes it more competitive if the scores are close because having one person suffer a random “win becomes loss, can’t be fixed” or someone not being able to play for whatever reason won’t cost you the war.
The current system is too constraining.
Even if our members like GW, it is taking too much time. We currently have several members “on vacations” in some guilds in lower brackets. And if anything happens to anyone in RL, the whole guild gets penalized. And there are always unexpected things happening in RL… and people should be allowed to just not play one week if they don’t feel like it without having to have to leave their guild.
It has been asked many times. Even if there are many different views on what should be done, it seems that a good part of the community of the forum is in a favour of a more flexible system.
Now we need the devs to react on that topic… like on many others, unfortunately.
27 or 25 both seem good. Both seem a lot better than the current one.
I voted 25 but 27 would be OK. There’s so many reasons why full 30 participation is a bad idea and so many more reasons why partial participation is a much better idea.
Holidays
Family commitments
Work
Bereavements
Stress
Etc etc etc.
The current system is inflexible and far too rigid, some would say broken.
27 would be a good number.
Anything much lower than that gets close to penalizing more organized guilds.
I would be fine with 25, but that would be the absolute cutoff until it is too many omitted.
I voted 25 because as @Tacet said that would be the lowest i could agree to
25 also,but it would be fair for a guild to receive a reasonable bonus points if more are participating
20, weekends should be free
27 or 25 are both good and seem a lot better than 30. Real life and players that hate gw would have their spaces.
No 1 member option?
Now you’re talking ZK! Might be time for me to make a comeback.
Are there any guilds that allow a player to sit out for idk… forever? Asking for a friend.
25 is a fair number which allows for absentees for whatever the reasons are.
My fear with 25 would be ties. It seems like it’s harder to get variability in results the lower your go. At the very top, one person losing one match can be a difference maker. In some ways that becomes more extreme when fewer scores matter.
There are on PC/Mobile. On console, I hear there is now one on X-Box that is recruiting serious players for a non-GW guild. On PS4, I think Crimson Sky is the highest ranked guild that advertises on the forums and is GW optional, but we only do 2-3 guild statues per week, so we’re still a little on the casual side.
I honestly think there is a huge opportunity for a first-mover on both consoles to attract hardcore players who don’t like GW. There are a lot of us who would find that mix extremely enticing.
I voted 25, but 27 would be great too. That gives a little bit of a buffer so people can go on vacation or deal with other life stuff without penalizing the guild in GW.
I still want Guild Wars, not Best of Guild Wars. 
Dominant on PC/mobile has several that just flat out refuse to be a part of GW and were OK with that.
I Voted for 27 (or 10%) the same number when this idea was originally put forth. I arrived at the number 27 originally in the proposal based on what the developers had done with the Guild chest reducing it from 45k down to 40k so 27 members could max it.