Stash, that all sounds great until you think about it.
Police get involved with mentally ill people because sometimes they have to use force to have a mentally ill person seen by a doctor and assessed. Police officers are vested with powers under legislation to help other professions.
Homelessness and school discipline are already not police issues. As for neighbour disputes, what kind of minor neighbour disputes will these professionals be mediating - noise complaints?
How will a non-police officer enforce laws on excessive noise or trespassing, or lewd conduct, or a myriad of other offences?
Everything you have said will wind up being investigated by police anyway.
Who will be enforcing traffic laws and investigating traffic accidents if police will only be trying to reduce crime?
These are all traditional police jobs for a reason. Defunding the police is defunding the police, and it's unworkable.
Less police will mean the police employed will be overworked and susceptible to stress leave, leaving less even police. Meanwhile, community expectations from their police will be met even less, leading to more distrust and more disrespect towards police.
They need more funding, not less.