Addon Domain: Manage Subdomain(s) Only, not the Primary Domain

I have an account, my main account, let's call it Blue and it hosts blue.com on IP 1.2.3.4 (for sake of example). My friend has a domain on their own server, let's call it buddy.com (for sake of example). We want my server to handle all wildcard domains (*.buddy.com) not already being managed by buddy.com's DNS, specifically on the Blue account because that has all the software and environment on it we want to handle *.buddy.com's traffic. We also want SSL enabled. I'm really close to figuring this out. Here's what I know I need to do:

• My friend adds DNS records for buddy.com: *.buddy.com 1.2.3.4 300 _cpanel-dcv-test-record.buddy.com ns1.blue.com 300 _acme-challenge.buddy.com ns1.blue.com 300
• I add all of buddy.com's nameserver IPs to "Configure Remote Service IPs"
• I go into the Blue cPanel account and... somehow magically (this is the part I can't figure out) only add *.buddy.com as an addon subdomain and configure it do the subdirectory I want to handle its traffic
• I install the letsencrypt plugin for AutoSSL and run it for the Blue account

Now I can accomplish this if I add buddy.com as an addon domain with all of the subdomain and DNS configuration that comes with it including www and webmail and cpanel etc etc and then add *.buddy.com as a wildcard subdomain, but ***I don't want*** the server to try to manage the buddy.com primary domain, I only want to manage the wildcard subdomain. Is there a way to do this properly? If not, to what extent can I edit the DNS records and remove all the crap I don't want? How else can I trim this down to configure only the minimum necessary to accomplish what I want?