Hello, thank you for the opportunity, I have gone through the project description and understand fully what you are trying to archieve. I am a system administrator with over 5 years of experience managing 250+ servers with over 40,000 websites hosted on them, mostly cPanel servers.
From the description, I see you have an app that creates subdomains using the cpanel API and you need those subdomain to be live immediately. I have a number of ways you can go about this, do reach out via the chat so i can share some of them with you.
Also to add, i have done this in a number of project which works absolutely great and all subdomains created are live immediately and have SSL configured for them.