I like content designed for many people. As others have mentioned, people already have to be excluded from content such as NMs with a 15 cap. Of course that's always going to happen with any cap, but lowering it just means more people excluded. Then again my linkshell could easily form two strong 8 man groups. Problem then is there's only five NMs and only one that always spawns at night.

Still, for upcoming instances I don't want to miss out if we have for example 10 people turn up. I don't see why an instance can't be designed for a dynamic number of people, yet still limit the individual fights within it to only being claimed by one party. That way you don't get 30 people slaughtering a mob, but 30 people can still come and play.