(This is an excellent example of why the "defund" slogan is confusing; however, of the other suggestions I've seen in this thread, I haven't seen any that make clear the level of change that's needed.)
I can think of a few things that will require more money: better/longer training for officers, and doing more investigations into citizen complaints. That stuff isn't free.
When you defund an organization and at the same time demand it does better, you create a siege mentality among the members of the organization. They will get worse, not better.
Why should we subsidize their training?
Furthermore, maybe we make sure cops have 1 vest, 1 badge, 1 gun in a holster, ammo, and 1 tazer. Ban assault rifles, use USED cars, get rid of tanks, armored vehicles, etc... Get rid of tear gas, and explosive ordinances. Basically take away a LOT of their toys.
So gun, car, badge, uniform, vest, payroll and that's it. No paying any money at all to unions. Maybe even save some money for performance bonuses if they can lower their brutality outcomes as a collective body. Cops w/out any reports get like a 5k bonus at the end of the year. 20k after 10 years, etc...
And whilst you're building a new police force from scratch, who will be doing the policing in the meantime? Who will be appointed to create this new police force and how will they be chosen? What will they do the first time one of their new police officers gets shot? What will the city do if the brand new police force is incompetent because none of them have any experience? And then if they decide to unionise too?
Rebuild it from scratch rarely works out well in software. It's hard to imagine it working better for an entire police force.
That said whatever they did and whatever it was called, it apparently worked. But I wonder if that was due to this re-culturing vs the more practical aspect of using body cameras.
Firing and re-hiring everyone, legally and contractually, lets you get rid of the existing union and work on building a new one that's actually focused on what a police officers' union should be focusing on: protecting good police officers from abuse and corruption from above, negotiating salaries and job conditions, etc., much like any other workers' union.