I hate to divert from the awesomeness of attempting to mod an MD enclosure, but what problem are we trying to solve, here?
If noise is the chief concern, just yank out the disks and install them in a custom enclosure with an appropriate disk controller(s). If DAS level IO is required (or preferred), then they'll obviously need to be installed into the system consuming the storage. The other (cost-effective) alternative would be to host it out as NAS.
Of course, if we're throwing money at the problem, we can get into adding HBAs to the custom enclosure that can give you something like DAS performance, and would be a pretty cool experiment into SAS/SCSI topology hacking (unless someone more knowledgeable than I has actually done a DIY DAS).
Either way, my opinion is that you're better off throwing away (or selling) the enclosure itself unless you're willing to operate it in enterprise-like conditions (such as a home rack). It will fight you at every level if you try to use it by letting it sit under a desk somewhere. It's big, it's loud (even the drives themselves), it has special cooling needs, it's a rackmount chassis... etc.