I agree, Celtic Roundhouses do look pretty awesome. I think the thatching would be the biggest obstacle though--most of us are unlikely to have the opportunity to learn that skill from an expert. I've seen pictures of other kind of European shelter that look easier, and some definitely seem more portable or less permanent.
Both Jesse and I have been collecting photos of prehistoric huts, benders, Sami houses and tents, gypsy tents, and so on, on pinterest. The sod or turf huts are my favorite, but I wonder if we have too much rain to make those practical here.
BTW, I love the parallels between some of the European and North American dwellings. Obviously laavus and tipis are closely related, but the construction of the bender tent appears identical to that of the wikiup.