Okay this is going to be hard to explain, or at least harder to explain than why it is easier as Andrew says treat it as an rgb (CMY) device.
The volume of the rgb numbers leave enough room for pretty much any combination of colors possible within the scope of any ink jets we currently use.
The PCS stands for something like Profile Connection Space is in almost every case these days L*a*b* for printers. The numbers go from your image in rgb to the mathematically equated nearest values run through a (grid) fixed precision LUT. Up until here all's well.
For the output side most profile packages do rgb or better CMYK.
Some top end packages will take this up to 12 or more separate color channels.
They are very expensive, take much higher training, and are seldom usable in system level drivers.
So are there any advantages?
Yes, but maybe as many disadvantages.
If you can control each ink independently you can have pure graduations with finer control of composite colors than if they PCS numbers have to be made composite and re-divided into the driver or hardware level color maps.
Yet when you use n-channel device profiles, Photoshop doesn't at this time use or preview N color profiles. You need at least 12 bits of precision in screening if you want to have any decent number of tonal separation. Because of this separate rips and or drivers are required.
I've always wanted to muck about with these, but had no RIP's capable of doing so. You could with the Canon I assume. I believe that the next operating system are able to handle both >16 bit driver level separation and N-channel device profiles too.
Before you had to work with plug-ins, saving out as DCS 2 files , RIPs etc to even get near this level reserved for high end offset or Roland printers.
Today it's looking like it will become easier. Just have to dust off my skills and re-read the Profile Maker guide.
Oh , yes most of the viewers will choke on esoteric profiles.