Here’s the thing: People lie to themselves. ALL. THE. F*CKING. TIME. Especially when it comes to money.
For that reason budgeting sucks the joy out of life for many and, like most diets, is doomed to failure from the outset.
So to save people from themselves build a forecasting engine that is solely powered by actuals (i.e. what they actually spent) rather than what they hope to spend, barring any unforeseen emergencies (which occur with monotonous regularity) or “one off” anniversary/birthday/Christmas/holiday spends. Project the future based on their actual past. Even better, make it mandatory without the option of switching it off.
It will be disheartening.
It will shock.
However for those willing to pay attention to the pretty charts and fancy reports, it is the thing most likely to change behaviours.
For bonus points readily support tagging of transactions/categories/accounts to allow standard “canned” reports like cashflow, profit & loss, etc to show slices of activity from a given rental property or business or whatever.