Sitecore PowerShell script to recursively reset the base template of all items under given path.

reset-base-template.ps1

Get-ChildItem "/sitecore/templates/Feature/Fortune" -Recurse |% {
$currentTemplate = $_
$templateIds |% {
$currentTemplate."__Base Template" = $currentTemplate."__Base Template" -Replace "$($.ID)|", ""
$currentTemplate."__Base Template" = $currentTemplate."__Base Template" -Replace "$($.ID)", ""
}
}
$templateIds |% {
$deletingTemplate = $_
Get-ChildItem "/sitecore/content" -Recurse | ? { $_.TemplateName -eq $deletingTemplate.Name } | Remove-Item
}