/alliance chat could be useful. Form a alliance could be a upgrade you could purchase from the birdsong Emporium. Forming LD & BN matches with guild and alliance members would be cool, maybe inspire guilds to play more Guild LD matches.

Perhaps allow one Guild Hall to transfer Guild crowns/items to another Guild within the alliance.
Perhaps at a slight cost, but definitely only by Guild Masters (even officers could abuse this system, so it's best left to GMs to make any transfers to another alliance). Think of it as a Guild Trade system, unlike players that trade with a click on the player character, Guild Trades would only work between alliances and the two Guilds would require a GM to be online and doing the transaction at the same time. (Unless gifting to another guild within an alliance is allowed.)
Further, due to the fact that there are no "wars" between guilds (unless you consider Guild PVP to be "wars", but that doesn't make much sense since there are no specific rewards to defeating another guild other than recognition) you could allow people to select "Party Open to Alliance Members" when going into the Clockworks (clockworks is not only Arcade, btw). This would allow you to choose one or more of: Solo, Open to All, Open to Guild, Open to Friends, and Open to Alliance.

And even further still... :D
Suppose that you wanted to have an AH specific to an alliance? Where only members of the alliance can use that AH. It would be stored within the existing AH, but a new tab would be called "Alliance Auctions" and would allow anyone within the alliance to post items for auction and only alliance members would be able to bid/purchase from that tab.

There should be a limit to how many guilds can join an alliance though, so that all guilds aren't joining the same alliance, and each Guild would need to contribute some upkeep (because OOO won't implement it if there isn't something like that, so at least it will be expected if mentioned like this) to remain within the alliance. (After a full week or two of no payment to the alliance upkeep, any guild not paying would be removed from the alliance automatically.)
To control who is allowed within an alliance, the creator of the alliance (Guild1 for example) would be titled "Alliance Master" (which includes Guild Master position of the member's current guild, but shows that the member has control over the alliance). Each guild that is added to the alliance must have at least one GM that is an alliance master. (As the seniority works with promoting officers/GMs so it would also work this way for the alliance, so that the creator is always considered the most senior member of the alliance guild masters.) These alliance masters would be able to promote other GMs to the position, however there is only one GM allowed to be an alliance master per guild, thus if the acting alliance master were to promote one of its GMs to the alliance master position, then the acting alliance master would automatically be removed from the alliance master position and replaced by whomever they promoted. (This makes for easy controls and prevents multiple GMs from the same guild from abusing power over the entire alliance.)

Phew, lots of thoughts, sorry if that was confusing. D:

Forming LD & BN matches with guild and alliance members would be cool, maybe inspire guilds to play more Guild LD matches.

You know with the "talking to each other" mechanism I posted earlier you could... talk to each other (I know it's a hard concept to grasp) to be on the same server and join the queue to be facing one another?

Perhaps allow one Guild Hall to transfer Guild crowns/items to another Guild within the alliance.

You cannot take out the cr within your guild but to use on your own guild. Why would it change?

Can we form a Horde?

Or a Panda?

This is Spiral Knights...

Can we form a Horde?

Or a Panda?

This is Spiral Knights...

There aren't even anything like "Alliances" (Essentially mega-guilds) in World of Warcraft.

~Sev

If you friend a guild, then you should be able to open and join parties with people from both guilds. But LD teams still remain strictly to the original guild.
A better idea would be a guild merge option for much smaller guilds with under 50 members. This way they will have an option to merge resources and decide which guildhall to keep and move in all the other stuff from the other guildhall. They should also be able to have an agreement between the guildmasters on the new guild name.

I support trading underwear wholeheartedly, I soil my techno-pants every time I see a Giant Lichen Colony ninja-rush me from across the room.

Wouldn't the word "alliance" kinda make it weird? Also, why do you need an in-game mechanic to do this?

Lol yeah, but I was kinda rushing out the door at the time (just read the OP, none the others). I can see where you're going with the whole social tab/more chat thing, though I'd be more happy if OOO would just let us create groups and chat channels. The whole trade thing seems kinda like it could normally just be done through normal chat, but sending your furniture and such to another guild sounds cool. BTW, you don't lose your stuffs if you stop paying upkeep. It just becomes inaccessible until you move it to an accessible area or start paying for the areas. I don't really have ideas for what to call them... I guess maybe just call them guild friendships?

I agree with him/her all the way with this. Imagine if the jeeps and echo of silence were allies and did this. They would have way to much. So -1 to this and graveyard this thread.