A clone environment would work, but it would have to always remain 'cold', which means whenever you change something you'll need to make sure you get a new set of clones. The most important thing will be protecting your database. What you could do is cluster SQL, and have the DR site act as a cluster replica. As the DNS name for the database connection would be the same from SolarWinds' perspective, in the event of a fail, you could flip the cluster, and turn on your cold instance (primary poller first), and it should just work....
You'll have to ensure that your clone pollers can reach all your polled devices over the same IP addresses for this to work, so your management network would have to span both live and DR sites, and you'll have to make sure any external access DNS (solarwinds.yourcorporatewebsite.com) has a failover IP in place too.
But, given the above, a cloned, cold instance would work and would be perfectly acceptable from a licensing perspective (IMHO anyway).