Example on how to use a class as a PowerShell splat value

PSClassSplat.ps1

class SplatClass : System.Collections.IEnumerable {
    SplatClass() {}
    
    [System.Collections.IEnumerator] GetEnumerator() {
        # This can be any hashtable stored or derived from the class. This is
        # just an example
        $params = @{
            Path = '/tmp'
        }
        
        $splat = $params.GetEnumerator().ForEach{
            # The pipe to Write-Output is key to add a NoteProperty for a str
            # "<CommandParameterName>" is used by pwsh in an array splat to
            # identify parameter names from values.
            $key = "-" + $_.Key | Write-Output
            $key.PSObject.Properties.Add(
                [System.Management.Automation.PSNoteProperty]::new(
                    "<CommandParameterName>",
                    $_.Key)
            )
            $key

            $_.Value
        }

        return $splat.GetEnumerator()
    }
}

$obj = [SplatClass]::new()
Get-Item @obj

Another option is have the class implement IDictionary and just return the hashtable enumerable for GetEnumerator() but that requires a few more methods to be implemented. Instead this takes advantage of a an array splat and the <CommandParameterName> note property to differentiate between parameter names and their values.