I wouldn't recommend to try it, as it will pretty sure crash the server or will make it at least unstable.
If you still want to try, you have to know the following:
Every variable does have its limits. You have prolly 3+ variables inwolved with the money. First of all: The DB itself. You can set a variable for each column. No big deal.
The next thing is prolly the stored procedure, which has to be adjusted aswell.
I don't know with what kind of variable the gameserver is working but in early 6.3 there was the arithmetic overflow while using the warehouse. So if you are running into the limits would will prolly get negative values and the gameserver crashes. The next thing is, that i don't know the variable the client uses. So you can see, you can't just set one option and everything is alright.
Why don't you just use those gold ingots? Or just work with lower gold values? This is much easier