There is one more release before guilds that is waiting on some front end work (the backend is in place already) that will generate individual colors for every alien, along with the ability for players to name their aliens. That might be a chore for a large household like yours, but it will create some fun narrative possibilities.
And then yes, guilds (no timeline, but we are working on it already). Guild member caps will generally grow pretty slowly (their blueprints will be pretty easy to get, but planning office levels are always a limiting factor). You have a strong head start on planning office levels, so you will probably be able to grow your guild member cap quite fast.
Guilds can be setup as either open access or application required, so setting yours as application required would allow you to gate it based on whatever criteria you want. Using yours to help LBI holders get a strong start is a great idea.
I won't be worried about the size of your THREE account in game
Honestly, the best configuration will be for each guild to have a whale anchor, surrounded by minnows, unless they want to challenge other guilds with development contests where size is an advantage. Within a guild, workers attempting to read blueprints or build will use idle residence slots from smaller guildmates with extra before using their own slots (and part of the burn will go to their guildmate instead). This lets the whale use their own slots for quests, while providing their smaller guildmates with an extra stream of THREE in-game that can help them make faster progress on growing their households and unlocking the various different blueprints and buildings.
There is some sybil risk, but we think it's a powerful way to help smaller accounts grow quickly without costing the larger accounts anything extra.
As top of the leaderboard, I am wary of building a guild stacked with top accounts to dominate too much
Some of the guild buildings that will be available later will have powerful benefits that might be worth creating a whale guild to level up more quickly, but we think the benefit of borrowing extra worker slots from small guildmates will be more valuable. We will keep an eye on that balance as new features are added to guilds over time. Right now we're just trying to make it more fun and engaging, and we think guilds are a big step in that direction.
Also PVP will be non-destructive and opt-in, though a later release may have guild leaderboards with scores based on PVP challenges completed instead of strictly based on household size. Guild leaderboards are not planned as part of the initial guild release.