Ya, if your doing this professionally, you're better off getting something professional. The route your talking about going sounds like it would be more headache than its worth.
I've used ICYDock products with lots of luck, and my new favorite is IOSafe. The IOSafe guys have optional RAID capable enclosures with USB 3.0. All of their enclosures are fireproof and waterproof and come with a warranty that covers the cost of disaster recovery via a major professional recovery service. It would be well worth the investment if you rely on your data for a living. I've used these for on-site backups when off-site was just not in the cards.
This is one of their flagship products with RAID... its a NAS but I think they have direct connect option on other similar units. They will put 2 x 4TB drives in this sucker and give you the option to upgrade them to "Enterprise" drives. Bare in mind these enclosures are designed to not be opened and have drives replaced. You can do that (I've got it before) but you'll probably loose the fireproof/waterproof ability of the case.https://iosafe.com/products-n2-buy