Is it possible to use custom buttons available in the Show-InstallationPrompt function to offer the user an Install and Uninstall option using these buttons to drive the code?

You could do it in Deploy-Application.ps1 by placing this line:

Show-InstallationPrompt -Title $installTitle -Message 'What do you want to do?' -ButtonRightText 'Install' -ButtonLeftText 'Remove' -Icon = 'Question'

Before this line:

If ($deploymentType -ine 'Uninstall' -and $deploymentType -ine 'Repair') {

Thanks very much, will give that a try.