If done properly, I'm not opposed to the idea, so long as the original version is always available.
Personally, if I had the money, I would pay to convert flat elements on lost 3-D films, such as TOP BANANA and BANDIT ISLAND.
Not crazy in the least. I saw the latest G.I. Joe movie in 3D and compared to the not-ready-for-prime-time results on some other conversions, I walked away rather impressed. Stereo D have really upped their game in conversion, and I would love to see them not only tackle conversions for films like the ones above, but also optimise native 3D from the classic era.