Would it be profitable to manufacture and sell my new mining hardware?
Depends on whether you can bring something to market that's better than what's already out there. I'm not sure how quickly you can set up something like that, but 200GH/s for $99 right now would probably sell decently. 12 months from now, probably not so much.

This is really an economics question you have to answer, and we'd need a lot more information about your costs and market in order to assess the opportunity properly.