When I run with my Guild-mates We usually keep some kind of running bet. Always small amounts and always things that are easy to track. Like first one to the party button gets 250cr from everyone or first one to die pays 250cr to everyone. Its keeps things fresh.
It would be nice if we could implement this officially so that everyone could enjoy it. It would be an advanced party option that anyone could access unless disabled by the party leader. Once the bet is made, the others on the team will get a notice explaining the rules and the option to accept, hide, or refuse; similar to an invite.
PvP is coming out pretty soon, and with it contenders will pay a specific amount of crowns or CE to participate in rounds that will grant them rewards if they win. That's the equivalent of your system, only not exploitable nor encourages scamming. "Hey, you have to accept the bet before we continue." "Huh? What's all this stuff to read-" "COME ON YOU'RE TAKING FOREVER." "Fine, fine..."
By the end of the run, the new party member is wondering why he's missing 5000 crowns.
Gambling shouldn't be allowed on Spiral Knights outside of official Spiral Knights events or features.