WebDeploy 3.5 supports customizing App_Offline.html via an App Offline Template option to msdeploy. Example:
msdeploy.exe -verb:sync -source:iisApp=sourceApp -dest:iisApp=destApp,appOfflineTemplate="App_offline-template.htm" -enablerule:AppOffline
In a publish profile I can specify -enablerule:AppOffline via the option
<EnableMSDeployAppOffline>true</EnableMSDeployAppOffline>
Can I do the same with appOfflineTemplate ?
Currently not possible. Read more at: https://aspnet.uservoice.com/forums/41199-general-asp-net/suggestions/6619898-enablemsdeployappoffline-appofflinetemplate