Often, whenever factions put together projects, it boils down to each member having to go the bank and draw from his/her account and "pitch in" to the effort (whatever that may be). But, most real organizations that I know of have their own teasuries of money to spend on organization goals and projects. Sure, the money comes from members and donations from nonmembers, but there is a difference between the money belonging to the organization, and the money belonging personally to each member.
So, I propose a faction "bank" if you will. It would function much as Sanctuary's bank, with the following exceptions:
There is only one account in the treasury. So any money donated to the Seeker treasurer goes only to the Seeker vault or account.
Only members of each organization could withdraw money from the account. Responsibility for withdrawing would be left up to the members individually. Obviously, stealing funds or using them incorrectly, if noticed, would be punished by the leaders of the faction and other members. But unless the member lacked common sense or was purposely going against the faction, these funds would probably be spent correctly.
Another element of the treasury would be that anybody could donate to it. So a person could give money to the NPC treasurer, or put money in those donation pedestals which are in so many of the faction houses. This could prompt fund raisers by organizations, and also make donaters feel like they are tangibly adding to those they are supporting with their gold when they give.
What purposes would the treasury be used for? Well, projects such as construction or expensive events that are for the good of the organization and agreed upon by its members could be payed for by the treasury. Raising dead members of the faction could also be an expense, as well as paying for more mundane things, such as taxes, and equipment. Perhaps there is a system in place why deducts a certain sum each week from the treasury representing faction upkeep? This would give some short term goals to faction members who need to support their group which has taken them in. This is only an option though. Of course, players support the factions in so many other ways.
In conclusion, the treasury would make the faction feel more powerful and capable of taking care of itself. As a member of a faction, I do not know right now what its financial situation is, and am constantly reminded that all projects I may undergo for the faction will come out of my character's personal bank account. Yes, this system is somewhat superfluous, but would also add a deep element to factions -- Bookeeping!