Nameserver and cPanel DNS Only issues.

Hello Everyone!

I got some great help on a question that I got here before so I have come back with another slight issue.

I had 1 Namecheap domain. This domain had it's own custom nameservers:

ns1.domain#1.tld
ns2.domain#1.tld
ns3.domain#1.tld
ns4.domain#1.tld

Now this domain pointed to it's own custom nameservers

Here is what my configuration was:

hostname.domain#1.tld WHM Server

ns1.domain#1.tld cPanel DNS Only (VPS Arizona)
ns2.domain#1.tld cPanel DNS Only (OVHVPS Canada)
ns3.domain#1.tld cPanel DNS Only (VPS Texas)
ns4.domain#1.tld cPanel DNS Only (VPS France)

At this current setup, I could never ping my NS servers on their hostnames "ns1.domain#1.tld",
I had to create separate records "dns1.domain#1.tld" instead. I talked it over with NameCheap and they recommended to delete the Nameservers and A records but that would mean downtime for my clients. Now I have bought a second domain so that resellers can use whitelable servers. I changed all of my NS and server hostname to ns1.domain#2.tld.

I currently still have my clients use the old nameservers which point to the same NS servers but the official NS is on domain#2 now. My question is, is it possible to have my clients use domain#1 NS for shared website clients and domain#2 for reseller clients? Or should I just have all my web clients use domain#2 and resellers can point their own NS A records to domain#2? I would like little to no downtime on this as I want to keep services up and running.

Thanks in advance!