I was reading a forum post about making guild vs guild more fun, and then I remembered what our guild was doing: a Tier 3 Lockdown Tournament. The forum post I read is the first link below.
http://forums.spiralknights.com/en/node/30472

We could have an event hosted by OOO: a pvp tournament that occurs once every season (3-4 months). Something like the tournament found on the link below, but at a larger scale.
http://forums.spiralknights.com/en/node/28921

The prizes would be given to teams finishing 1st through 4th, and the prizes would mostly be accessories, unique armors, and maybe cr and ce. Yes the potential problem of ce and cr raises are there, but they're only given the to the best 4 finishing guilds, and the prizes would be equally divided amongst the players participating within their guild. Besides, we could also place an entrance fee of 2000-3000cr PER GUILD to have a slight crown sink. The 200cr per player to enter would still apply.

Format: 32 teams. 8 groups of 4. 6 matches per guild during the round robin. Each guild fights their group opponents twice, like in the UEFA Champions League. The top 2 teams in each group will move onward to the next round, fighting each other in a two-leg knockout stage until the finals.

Scheduling: That's the toughest part to this. The participating guilds must be active. OOO could set the dates for the 32 participating guilds and make the guilds follow it. Make it so that the tournament is held at times when the most players are online (summer or winter holidays?). If a guild can't get the team ready before the match time, they've forfeited the match. The matches go by really fast anyway (6 minutes at most) so if every match were to be played, the event can easily be finished in 2-3 weeks. Besides, the tournament can be scheduled either annually or once every 6 months so that guilds can play friendlies with each other and get ready for another tournament.

Qualification and Seeding: Another tough one. Qualification is mainly done by the 2000cr entrance fee and for the first 32 guilds that join the tournament. I'm trying to think of a qualification round right now, but I think that would be too large a scale. Now seeding. The all-time rankings would be great for this because seeds can be appropriately created for the participating guilds. The top guilds that are participating can take the 1st seeds and everyone else becomes unseeded. Then there would be a random draw using a generator. As a result, evenly balanced groups and maybe some groups of death to make the tournament more interesting.

Well, this was just an idea that occurred to me when participating in a trial-tournament with other guilds to make Lockdown and pvp more interesting overall.