No I see no massive improvements. My other consideration is that I'm not aware of the full extent of the changes for the new estate and economic system, and whether these changed proposals will remain relevant at all in that context. But really nothing here is compelling enough to make me think it would be a priority, and in that case I would rather see how the game develops with other proposals that are in development.
This idea has SO much potential. The most beneficial one that I can think of right now, would prevent what Chenier said happened to Paisly (which I witnessed by the way, it was not pleasant). A vault idea can show you daily changes to tax collection, maintenance costs, predicted knight tax share, trade balance, etc. As it stands, there is no simple way to track a trade balance and predict these maintenance fees. I know I've had to bust out the calculator a few times to do some number crunching. I mean, as it stands, you won't know if you bankrupt your region until taxes are collected. And if you ARE about to bankrupt it, or the militia will auto disband, etc, why not have a system in place where the region lord will have a chance to prevent the disaster by depositing the 150 gold he was saving for the next block on his new walls?
Also I rather enjoy the notion of the lord having a mechanic available to segregate gold he intends on spending on himself and/or sending to his family from gold he wants to use on the region. I've done some mental math on that one, then forget how much I spent and on what, so end up waiting for more taxes to come in so I don't find myself broke.