In reply to ford23:
I've been having similar thoughts and found this
http://korpijaakko.com/category/vatnajokull-2012/
interesting reading
There's an account of a vatnajokull trip in a Nordic ski tour memoir called "Taxi for the snow line", although the prose style wasn't worth shelling out for a new copy. eBay maybe?
I can't tell you anything more other than informal chat with a guiding company in Reykjavik indicated a Nordic tour was a distinct possibility but that Iceland lacks the hut system which makes Norway an attractive option.
Lonely Planet Iceland said pretty much point your skis in any direction and go for it but don't expect to hire gear in-country. I expect the numerous Reykjavik guiding outfits could give you more nuanced advice.
There was a salutary tale in the papers at the start of the year of some rather over optimistic students getting rescued three times on a south to north Icelandic epic.
Unlike Norway I think public transport to the start point would be tough to find in winter. Private hire would do it, again guides in Reykjavik will help.
Iceland, like Norway, is wonderful and very very windy.
Good luck.