First stab at translating functions.

1-FunctionTranslator.ps1

    param(
        [Parameter(Mandatory=$true, Position=0)]$key
    )
    Write-Verbose "Attempting to establish new function '$key'"
    $keyParts = ($key -split '-')
    if($keyParts.length -gt 0){
        $validVerb = Get-Verb $keyParts[0]
        if(!$validVerb){
            Write-Warning "'$($keyParts[0])' is an unapproved verb which might make it less discoverable. Use the Verbose parameter for more detail or type Get-Verb to see the list of approved verbs."
        }
    }
    Write-Output "Function:$key"
}

function As{
    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true, ValueFromPipeline=$true)] [ValidateScript({$_.StartsWith('Function:')})][string] $funcKey,
        [Parameter(Mandatory=$true, Position=0)]$function
    )

    $funcImp = "Function:script:$function"
    if(Test-Path $funcKey){
        Write-Verbose "Original function: $funcKey"
        Write-Verbose "Implemented as: $funcImp"
        Copy $funcKey $funcImp
        Write-Verbose "Copied: $(Test-Path $funcImp)"
    }
}

1-implementation.ps1

# define functions
function Invoke-Nunit($param) {
    Write-Host "Nunit: $param"
}

function Invoke-Xunit($param) {
    Write-Host "Xunit: $param"
}

# register as specific function name
Register-Function Invoke-NUnit | As Invoke-UnitTests

# invoke new function
Invoke-UnitTests -param 'C:\path\to\unit.tests.dll'

2-FunctionTranslator.ps1

function Rename-Function {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true, Position=0)] [string] $key
    )
    Write-Verbose "Attempting to establish new function '$key'"
    $keyParts = ($key -split '-')
    if($keyParts.length -gt 0){
        $validVerb = Get-Verb $keyParts[0]
        if(!$validVerb){
            Write-Warning "'$($keyParts[0])' is an unapproved verb which might make it less discoverable. Use the Verbose parameter for more detail or type Get-Verb to see the list of approved verbs."
        }
    }
    Write-Output "Function:$key"
}

function To{
    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true, ValueFromPipeline=$true)] [ValidateScript({$_.StartsWith('Function:')})][string] $funcKey,
        [Parameter(Mandatory=$true, Position=0)]$function
    )

    $funcImp = "Function:script:$function"
    if(Test-Path $funcKey){
        Write-Verbose "Original function: $funcKey"
        Write-Verbose "Implemented as: $funcImp"
        Copy $funcKey $funcImp
        Write-Verbose "Copied: $(Test-Path $funcImp)"
    }
    Write-Output $function
}

function WithAlias {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true, ValueFromPipeline=$true)] [string] $functionName,
        [Parameter(Mandatory=$true, Position=0)] [Array] $aliases
    )
    $aliases | % {
        Set-Alias -name $_ -value $functionName -Scope Script
    }
}

2-implementation.ps1

# define functions
function Invoke-Nunit($param) {
    Write-Host "Nunit: $param"
}

function Invoke-Xunit($param) {
    Write-Host "Xunit: $param"
}

# register as specific function name
Rename-Function Invoke-XUnit | To Invoke-UnitTests | WithAlias 'test'

# invoke new function
Test -param 'C:\path\to\unit.tests.dll'

Written because of this poshBAR issue