Why not use the taxes that people pay each month as well??
That money goes straight to the Argonath bank and it can't be dragged out. Remember that one time the economy went on foreclosure because the money was not flowing and all bank accounts were deactivated? There's a risk that might happen again if we intend to extract funds from there. The economy is dynamic and the money is always in constant movement despite everyone thinking that there's a script to spawn cash, this has not been possible since RS4.
So, basically make state funds accessible by the mayor and give them the chance to allocate funds? So long as the FBI or whatever government institute can have control over it, so that it keeps stuff interesting :p
Part of the mayoral funds are do planned to be used for this future organization since they are part of government aswell. However, as you've already said, a mayor alone should not have total control of said money but rather they will be able to vote and suggest to where such funds should be allocated.
The organization and the mayors will work together along with the new government rank which is the Governor (TBA) to decide the best way to make use of the money including the distribution of funds for businesses.
Its just gonna look like that one group is gonna be funded. Like c'mon, there hasnt been a winner that wasnt affiliated 
I'm pretty sure that everyone who decides to apply for mayor will not let their affiliations influence their decisions, as it would be considered poor handling of funds, which means corruption. And while having an active court leader along with the new FBI director it'll be only a matter of time until said person gets removed from his position.