As the title states is this something that is possible to do under modern OS X?
You mean on a hackintosh? Or real Macs?
On a hackintosh, the installation guides require disabling VT-d (if the CPU supports that feature) in order to install and run MacOS. If VT-d has to be disabled then I don't think it is possible to use it, right?
I have VT-d enabled in BIOS and have dart=0 removed and the machine is working just fine. I can't find one person who has actually gone out and done this but have seen many who have made it work under Linux.