Here is the current set up (in a nutshell).

The site is set up with a wildcard subdomain, so *.website.com is accessible. Clients can then domain map their own domains with an A record to the server IP address and it will translate the to appropriate *.website.com with re directions and env variables in htaccess.

Everything is working perfect... but now comes the problem.

The site has grown larger than a single DQC Xeon server can handle at peak times. Looking at cloud options seems tempting, but clients are pointing their domains to a single IP address with the A record (our server).

Now, this was probably bad planing from the start, but the question is, if this was to be done today, how would we set it up so that clients use a CNAME perhaps to point their domains to our server rather than an A record. And, if that is not possible for the root domain, how can we then use multiple IP addresses on our side to translate the incoming http request?

Complex enough? Hope I've explained it well!