Arshdeep,
Great idea.. using 0-100% rather than 0-1 would be bliss for us old school guys ;-)
In general using 2 decimals instead of integers doesn't make that much difference for most CMYK designs. Most of the upper and lower values are not reachable for the press anyway. For instance many digital print machines won't print values lower than 10% and stop at 90% at the default settings used by the print shops.
On topic of hexachrome and spot colors.
Only the very high end of the print work scale as used in my native country of the Netherlands, spot colors are default for any corporation that wants to be held serious. KPN for instance even tried to patent their colour green some years ago and they will pay the extra layer of ink without blinking. Hexachrome is a pretty basic use in glossy magazines that actually often add another layer of varnish to it as well as spotcolor. Direct to plate with stochastic rastering is not uncommon either. I've got an Uncle running a 6 color Heidelberg with an additional varnish extension who specialises in Art related books in Holland and that is mainly hexachrome. It is not a large market, but highly lucrative and relatively stable, unlike the lower end of printing. I personally have been doing print since 1993 and I've seen it all pass the revue.
Holland may be a bit of a exception to the rule, but it has been a leader in print technology since the 1600's when all the forbidden stuff was printed there. Design is an export product as much as taters. If Inkscape would support CMYK natively, rather than having to use workaround with the export so you can check while doing the design it would make it a more useful tool. Late binding puts the responsibility of error correction at the desk of your printer as well and most designers I know want to be able to do that themselves. Using color proofing printers and using screen callibration machines to get the whole design department on the same level. Those are not companies that are scared to spend a buck or what on tools and equipment as they also are paid in due for the use of it.
Now sure, Inkscape does not have to pretend to operate on the same level, but if it is possible to support the basics I'd say it should be a consideration. I'd love to be able to do a color seperation in Inkscape in a similar way as I can in Coreldraw for instance, so I could check the output raster of my original Magenta raster with what is actually being printed in the print shop. Currently that is a tad cumbersome.
My 2 Feng,
Jelle