I think there is quite big market for this kind of plugin. Many web devs will be interested it's just a matter how to reach those people. Old themes have been sold so many times because they have had time to find a way to their clients. Create a good product and let people hear about it. Step by step you will get wherever you want although it takes time.Well, I did think about doing a lifetime license (one time payment) but figured there wouldn't be enough interest in the plugin to make it worthwhile.
My market consists of people like you and the Babiato community, which is necessarily smaller than the market for, say, any old WordPress theme. But! The time limited deal interests me... and I would definitely be open to such a promo for Babiato members (I just need to look into the forum rules on such things.)
I would send a message to @Tomz he is an admin of this forum and also a cool guy. He will help you to promote here.Is there a section of the forums for RFCs like that? To gauge interest?