Re: So whose bright idea was it in the first place?
They ended up on Oracle, that's all you need to know.
You only end up on Oracle when you have absolutely no sense, control or idea of what you're actually doing, what that requires, and what the best way to implement it would be.
My concern would be why is this some sort of bespoke project rather than just what everyone else uses for the bog-standard business practices (ERP, HR and bank reconciliation? Gosh, if only there were other places who needed those!).
I am of the opinion that government projects should come with a fixed deadline less than 5 years, a fixed budget, six-monthly audits on progress, and the project terminated if it doesn't mean two of those audit's expectation. And all projects should have that requirement. You want to bid for government projects? You better get on board.
If you can't do something in 5 years, or you slip for more than a year, you shouldn't be doing it.
This place actually seems to have a decent handle on things, for a local government project. "This isn't working, we want to know when it will work, how much it will cost, or we'll cancel it" should be the norm.