Can I create the following CNAMEs with "mydomain.com" to effectively whitelabel "mydnsprovider.com"'s nameservers?
ns1.mydomain.com CNAME --> ns1.mydnsprovider.com ns2.mydomain.com CNAME --> ns2.mydnsprovider.com ...
I think you should be setting ns1 and ns2 up as A records instead of CNAMES, but either way, anyone performing a DNS report on a domain that uses your 'white label' nameservers will see that those are not the real nameservers, as some errors will be detected.
Your DNS provider will need to assist you in creating appropriate records for this to work the way you want it to.
I think, if this is what you mean, you are talking about private-label. This can only work if you add the Nameservers as another DNS record with its own IP's.
Let me explain. Lets take an example of a hosting company offering private-label hosting. The server, where your reseller account is hosted with your domain name, will have to be one of the NS names. So this server has the following:
ns1.resellerhostname.com -> ipofhost
and than yours: your1.nameserver.com -> ipofhost your2.nameserver.com -> ipofhost
So, this means the host has to add your nameservers, that you registered if your able (or your provider does this) to their server that they made availbale for you to resell.