Which again, goes back to raid size.
Back when I raided in WoW we had a core group that ran 10-man hard modes while also having raid nights were we'd run 25-man content. Your class leaders and the better players in the guild would be part of the core group while your family members and more casual individuals would run 25-mans (one of our core group members would bring his mom to DPS 25-man raids, for example). Here's the thing: they were effectively seeing the same content (Ulduar). Sure, the 25-man group was not pushing the big red button for Mimiron or killing Steelbreaker last during the Iron Council fight, but they were still seeing the same dungeon and meeting the same bosses.
I'll admit this modus operandi died when Blizzard merged raid lockouts (back then you would have one lockout for Ulduar 10-man and one lockout for Ulduar 25-man, allowing you to run the instance twice per week but for two different raid sizes), but it was still infinitely better than allowing the same instance to be spammed with super low drop rates.
Again, all you'd need is a 24-man mode for the content in question. If it turns out like anything that I've seen during the time I raided, you'd still have spots open to fill on raid nights (we used to ask friendly guilds if they had anyone that wanted to raid with us that week or, worse came to worst, PuGged). If you're worried about strict raid sizes I'd suggest SE lift the idea behind flex raiding from WoW.If there was no loot lockout / penalty, even keeping at a fixed 8 Player Raid, they could've joined and run w/ their FC via being rotated in for each raid:
* First team (8 players).
* Rotate in extra FC / LS / Friends that couldn't go the first run.
Instead, they are all forced to start finding their own static or just PUG / Party Finder each week.