i honestly like that idea better than building a fresh ecommerce solution. there are so many other options that are quite good and already command market share. in addition, as i kind of mentioned, pulling someone away from their established ecommerce solution is like pulling teeth.

plus, if you could develop this into a multi-platform plugin, you could probably use that process to develop a framework for developing plugins for multiple platforms and build some more, since you seem to have good ideas.

just a few thoughts. don't let me discourage you from running with what you have.