Have a replay mission fee, that increases every time you go to the lobby in increments of 100 crowns. Only party leader pays it.

Well, since everyone in general discussion is so concerned about it at the moment, I decided to propose this (it has been suggested a couple of times already but not the same way as me)
So, you can freely help newer players finish all their shenanigans in the missions, while the more popular missions will eventually break even with arcade versions and stop this awful practice of farming only first 1-2 levels. Also, this will help with player interacting a bit.
I think, crowns payout should be placed where currently materials in research daily missions is.
This raises the issue of not being able to finish the levels before the fee gets high enough (a - not enough energy for elevators, b - having beaten up or disconnected and returning to heaven, c - you just like to play this particular mission solo over and over again)
a) well, this can only be solved by employing the mission map somewhere on the mission screen.
b) tough luck, you got to find someone to help you (duh, this is what spiral knights is all about) or ask someone to be a party leader for you (finding someone of the same mission completion is always good).
c) pay the price, it's not that big, right?
This will only require using (№ of missions * size of int) memory space for each player - not that much; and simple coding.
I also think that expansion missions (OCH) doesn't need this, since we paid money for it, but it's up to developers to decide.
One more thing: if this system is to be implemented, please make sure to send an announcement mail, describing it in full detail.