I think that the Assassin's Guild needs improvement, specifically in how bounties work.
As it stands currently, they are horrible assassins and there is no reason to really hire them for anything except mechanical removal of a leader. If you actually want someone dead it is far better to pay another person directly, than to do it through the guild.
Why are they bad assassins?
They're scam artists. They will take a person's gold and keep it, even if the target is never killed. The bounty is also removed eventually, with no refund.
On top of that, the victim can pay their own bounty off.
There is no way an assassin's guild would function this way. I can't conceive of a scenario in which I hire them, they pull that scam and anyone ever takes them seriously or hires them for a job again, let alone the severe backlash they would face, immediately from armies of angry adventurers who have been scammed/robbed.
Imagine you hire a hitman, and they go to the target ... and the target just pays them more? Or they simply can't find the target for a month or so, so they give up and keep the money! That would be your last job, and you'd be lucky if you lived much longer after that. You'd likely need to change your identity completely, but one thing is for sure you would never work as an assassin again under that identity.
inb4 'tHey'Re rUnNinG a BuSinesS'. Yeah. Into the ground. You'd get 1 job before you need to rebrand and move to a new continent.
An assassin cannot be taken seriously, as a professional, if they will accept payment, never deliver and keep the money.
I really, really want to use this system but I just don't see any reason to. It's much better to hire people directly.
So my suggestion is a simple one.
1. Bounties cannot be paid off.
2. Bounties either 1. Last forever until completed or 2. Refund the gold if they expire and there is no kill (minus an effort/posting fee of 10%).