You can do this with:

set props("Address") = serverAddr
set props("Port") = serverPort
set props("MirrorConnection") = 1
set sc=##class(Config.ECPServers).Create(ECPServerName,.props)

And

set props("Server") = ECPServerName
set props("Directory") = ":mirror:"_mirrorName_":" _databaseName
set sc=##class(Config.Databases).Create(databaseName,.props)

Then you need the Namespace created pointing to that remote database and that can be done via the %Installer (I've not found a way of doing the above with %Installer but you can call class methods for the above from %Installer):

<Namespace Name="${newNS}" Create="yes" Ensemble="0" Code="${SourceCodeNameSpace}">
    <Configuration>
        <Database Name="${newNS}" Create="no" />
    </Configuration>
</Namespace