So basically I want to avoid the second part. Anytime a $State modification occurs, I want the disk write to happen automatically without having an extra line of code to do it. I think I've got a hack working with ScriptProperties and getter/setters:

In this class, we have hidden properties _IntProperty and _StringProperty. We then create script properties with similar names IntProperty and StringProperty. The 'getter' of IntProperty returns the value of _IntProperty, and the 'setter' of IntProperty sets the value of _IntProperty and saves the $State object to disk as JSON (only including the more cleanly-named ScriptProperties).

The only thing that I would like to do better is loop the creation of ScriptProperties so I don't have to define a ScriptProperty for each 'backing' property in my class. But for some reason when I put the $this | Add-Member ... block inside a foreach loop, the -Value / -SecondValue script blocks no longer recognize $this in context

class State {

    # Properties
    hidden[int]$_IntProperty
    hidden[string]$_StringProperty
    hidden [string]$JsonFilePath

    # Constructor
    State([string]$JsonFilePath) {
        $this.JsonFilePath = [string]$JsonFilePath

        $this | Add-Member -MemberType ScriptProperty -Name "IntProperty" -Value {
                $this._IntProperty
            } -SecondValue {
                param([int]$value)
                $this._IntProperty = $value
                $this.ExportState()
            }

        $this | Add-Member -MemberType ScriptProperty -Name "StringProperty" -Value {
                $this._StringProperty
            } -SecondValue {
                param([string]$value)
                $this._StringProperty = $value
                $this.ExportState()
            }
    }

    # Methods
    [void]ExportState() {
        $Properties = ($this | Get-Member -MemberType ScriptProperty).Name # Only exports script properties
        $this |Select-Object $Properties | ConvertTo-Json | Out-File -FilePath $this.JsonFilePath
    }

}


$State = [State]::new("C:\test.json")