Just as the title states, I believe it would be a nice addition to the game to have permanent weapon/trinket slots and multiple-use personal color change usables. They wouldn't be replacing our current temporary weapon/trinket slots or one-time use personal color change usables, but they would just be more efficient versions available for a higher price basically. OOO's you can decide that price yourself and suit it to what would be best for you to maintain profits as well as keep the economy balanced. Overall I believe that this would make a lot of people happy considering it's a bit tedious to have to keep on getting new weapon/trinket slots every 30 days or to have to keep changing your personal color every now and then just so it will fit a new costume of yours.
You really should consider doing this as it would really help out your one of your main marketing strategies with promotions bringing in new items and accessories to the game.
Here's another cool thread: http://forums.spiralknights.com/en/node/107077/
IMPORTANT: Before you post anything to argue against these ideas, read post #7.
If you're a forumer reading this, then please respond to the ideas above with your thoughts on the subject. The more support this thread gets, the more likely the chance it will be introduced and implemented into the game.