Government members, priests, armies? Really? What do they care for your guild? Even if you had powerful friends in on it, they'd probably never get away with using the realm's resources for your guild's aims.
In your own realm it's just a matter of asking the judge to enforce the oaths of your fellow nobles. If you get cheated through the bank by someone out of realm, well that's where the fun comes in. The more gold we tie up in the bank the more governments will have to bow to our wishes. Suppose we get really well entrenched and a realm judge isn't cooperating, we could expel their entire realm and seize all their assets in the guild. Is it really worth it just cause you're too proud to fine a delinquent debtor?
Closing guild houses: This also actually costs gold too. It'd also mean lowering the maximum full member count and reducing places where people can join the guild and interact with it.
No need to close them, just kick out the embezzling region lord. He can then spend his own gold to tear down the guild hall if he's that spiteful.
All of your solutions to making people pay is to spend a ton of money, basically, a ton more than what they owe you. By all means, try if you wish, and if you'll have fun trying to make it work, but you could basically do your whole scheme even more easily by keeping track of everything you want to do on a spreadsheet on your computer (and/or on the wiki), instead of using an IG guild. Suddenly: no upkeep, no taxes.
The problem with that is it's impossible to delegate responsibilities because I have no way to keep tabs on my subordinates. If I was just handing out loans myself it would be even easier to cheat me and I have nothing concrete to prove what happened. With a guild every single elder can see the same evidence I do that a branch manager is embezzling.
Guilds' primary use is for coordinating multi-realm military activities. Their secondary use is RP. Guilds with other activities rarely succeed in their aims.
I'm planning to spread the guild by offering accounts as a way to move money to the front lines. As for role play, people can now role play corrupt bankers.