The real practicality of a double-sided hub is to have another side if you strip out the threads on the first one. And that means you want fixed/fixed.
Truthfully, many people go around on double-sided fixed/fixed hubs and never flip the wheel. Certainly you aren't likely to stop, flip the wheel, ride a hill, then flip it back. And people with a fixed/free combination end up on one or the other but don't really flip regularly. The major exception would be if you tend to go hypoglycemic, cramp, or your derriere gets sore, in which case the ability to coast makes the ride home much more tolerable -- the freewheel is simply a bailout setup.
As for rims, riding a fixie on the road tends to pound rims a little more than a freewheel. Plus if you use the pedals to stop hard (or do skid stops and that kind of thing) you are torquing the rim more than on a road bike. So I don't particularly recommend light fixie rims. Anyway, is that really the point of a fixie? I'd go for a solid rim and not worry about it. I have one pair of low-flange hubs with Mavic T520 touring clincher rims, with Rivendell RolyPoly tires, just for a comfortable, non-slip winter ride. I have another pair with Open Pros, and then a couple pairs with old Mavic SSC Bleu's. The latter are a huge waste of good money, but they get lots of comments and look fine. But they aren't particularly light.