It looks like I may be in the minority in my thinking here, which is fine, but I just wanted to share that my experience was not the same as everyone else's. I do agree that the perfume pens are very appealing at first, that's why I bought one and know several other people who did. It's just that long term they didn't seem to stay very popular, at least among the people I know. So I'd be wondering if you'd get repeat buyers. And maybe that's not a concern, I just would think that if you offered something that people did want to buy over again, then you'd get the first time buyers and the repeats. You probably will get a lot of first time buyers, they aren't something that's available on every block, they are attractive and you can make them in attractive colors and everyone will know that their's is unique.
As for the concerns about ruining the finish, the CSUSA catalog has a perfume atomizer that they sell, item 050-7000, and according to the description, the vial is removable, to facilitate refilling and to keep contact away (from the brass parts is what they actually site). I haven't ever actually seen one of these in person, so my only concern about thinking it would be a better choice would be to think about if it would work for a woman to keep in her purse. It'd probably have to be turned a little different from the picture CSUSA shows with the atomizer, since that's more of a shape for sitting on a counter, but I don't see why it couldn't be turned to be more elongated and slim. But it may be that the perfume pen might win out b/c of that issue alone.
Just some ideas to consider.