Currently, MS-SQL Always-On is not supported as External Database.
Always-On technology is not supported by the point products (IM, IP, IG), so it is not supported by vApp.
Also, the SQL Windows Authentication is not supported by the point products (IM, IP, IG) and therefore not supported on vApp as well.
If the customer needs that vApp support MS-SQL Always-On, ask them to open an idea.