There are plans for something along these lines?but assassinations is not part of the idea.
Influence, will possibly be a commodity that will allow certain groups or people to (manipulate) things in their favor. This will not be something that is noticed in minutes, but would affect others over time.
Let?s say an adventurers guild opens a large (fort) near a town where a ?religious? guild is the only guild to hold sway. Since the adventurers do not pay any tribute to the clerics?they decide to ?influence? the locals to charge the members of that guild and others who do not pay a tithe to the church more then they usually charge?the more influence used the more harsh the charges, but the more apparent. In response the adventures guild might save all their influence simply to lean an election in their favor, or to have guards cost more for the religious guilds offices, while at the same time asking for war. All in all this is the basis of a political system. There could be more immediate uses, influence points might be traded for money or as payment?there are many possibilities.
But in essence this would allow there to be prizes to guilds for doing things, such as helping newbies. Having the best quality ratings on the things they sell, avoiding wars, never backing off from a fight?.the list could be endless. But this system is on a much higher level then ?get an assassin? specially since in our world assassination is not so permanent. It has little lasting effects, where as the right pressure put at the right time could make the largest of guilds crumble under their own weight. Priests, Merchants, Politicians, would be the main influence peddlers, and many of them can be bought in some way.
As many things this is way in the idea stages, but is an extension of the concepts we have for guilds.