I have stripped clear anodization off of rims and polished. Looks great, no issues. Black would probably be even easier to remove because it would be easy to see where the anodization hasn't been fully stripped.
Buy a pound of sodium hydroxide (you can get at a chemical supply store online), find a kiddy swimming pool, and mix with as little water as you can get away with. Drop the rims in, check every few minutes by rubbing the rims. When most of the anodization is off, scrub with a green scrubbing pad (I forget the brand) thoroughly. Your rims will look very dull. Then polish away, preferably with polishing compounds on a proper buffing wheel. You can get polishing compounds from Caswell; if you use their stuff start with the brown.
You can also do it with heavy-duty Easy Off (basically just sodium hydroxide in a spray-on foam), but that works best for small parts, might be tough to do a whole rim that way, although I'm sure it is possible with patience.
It's a lot of work but will come out very nice. I'm having anodization professionally removed form a set of Stan's 650B rims. Although I like poiishing its not an experience I care to repeat.
That is what I want to do, too. Transform a set of Stan's 650B rims into silver beauties. Perhaps paying a professional is the way to go. I would not want my kiddies to jump into a kiddie pool full of NaOH. I wonder how the 650B Velocity A23 (which apparently will be available in 2012, with a silver option) will compare to Stan's ZTR 355 in weight and durability?