These are easy ideas (easy for OOO to implement into the game). Before you read this please note I may have read someone's forum and accidentally copied some of it (it may be in my head) without knowing so please do not accuse me of plagiarism.
Easy Ideas:
1. Auction hall in guild room: (Bioxide suggested this in a thread)
OOO could just duplicate the auction hall from the Haven into the template they keep for all the guild halls (or whatever they do to style all the guild halls at once).
2. No more new bosses, but more games like Lockdown: (An idea I have had)
You may think I have gone crazy, but seriously what is the point of new bosses? Games like Lockdown are much more exciting as you can not finish them, you can not complete them. It is as if new bosses is like a racing car game - once you have finished it you hardly play it again, but Coliseum Games is like a game like Monopoly; you can not finish it! Anyway people still challenge vana including me for the cr and mats, but do you not think there are enough bosses? I reckon more people would prefer to play Lockdown than the Clockworks.
Not so easy but profitable ideas:
1. 5.5* Weapons: (An idea I have had)
My idea is that you could upgrade the types of damage/resistance etc. on some weapons for a price. Eg. you could increase the damage of Gran Faust so it will cause Elemental Damage (with different levels of course) or change the combo into a 3 shot combo. You may say this will make lockdown unbalanced. But lockdown is full of FFs, BTBs, GFs you name it. If this is implemented then people will come in with all types of equipment.
2. Customisation of Guild Halls: (Many people have mentioned this)
There could be training halls which you could purchase for a fee and more. My next idea is includes other suggestions for this idea.
3. Special shadow Lair Tokens: (Dagunner suggested this in a thread)
Making special shadow lair tokens is the easy part, but I do not know if making new weapons will be easy. Instead the tokens could be exchanged for equipment/guild hall customisations. Eg. 70 Rabid Snarby Tokens = 1 Rabid Snarby Training Hall.
Ideas which OOO should NOT implement into the game and knights should stop suggesting (no offence meant - even I made a suggestion about pets once):
1. Pets: (Many people have suggested this in many threads)
One word - Laaaaaaaaaaaaaaaaaaaag. Another word (well actually a phrase) - What is the point?. Another phrase - What are we going to do with them? I know they can aid you in battle but the game is easy enough since the update. It is unfair on us vana harvesters since the game is easy enough already since the update and it is unfair for people who have got slow network connections especially wifi people (I temporarily had to use SK on wifi, trust me, it was HORRIBLE)!!!
If you are reading this, OOO, please regularly check the suggestion forums, as people are posting ideas like these, which are really good ideas, for free.
Note: I shall update this forum with new ideas and if you would like to suggest any changes to my ideas that would be appreciated (I shall say who they are from). Thanks.
More Lockdown games seems like quite a reasonable way to get more content into the game.
Are you the guy who suggested Shadow Lair tokens in another thread? Shadow Lairs already give special materials. While materials are not the same thing as tokens, the two ideas seem kind of redundant.
You are correct that guild halls are terribly boring and neglected. However, your ideas for guild halls have been suggested many times. There is even a meta-thread that attempts to consolidate suggestions for guild halls.
Your idea for "5.5-star weapons" could be implemented by letting weapons have a new kind of UV: increased elemental damage, increased piercing damage, etc. I don't know whether this is a good idea.