As I said, I would be more than happy to upgrade to a Developer/Agency version. Most companies offering this range from $250/Lifetime to $199/year. I’m a one man development shop as well so I do understand making money.
I like your theme and what it offers with the add-ons. Simply put though, as a developer, I look for the way that I can do work for my clients with the least amount of resistance to their needs. I have several themes/plugins that allow me to re-use. One of the worst things I can do to a client is to say, I’ll build you a website, but first you need to go to vendor A, B, C and D to buy their plugins before I can get started.
Here’s some examples of other WP theme/plugin sites that are doing quite well using that sort of model.
Again, I like what you have to offer and I want to see you succeed and I’m willing to be your first agency client even. Those sites above are all doing really well, and your theme with the add-ons is a fantastic competitor with how customizable it is.
If you have a mailing list or Facebook group, I would encourage you to setup a poll to see how many would upgrade if you offered such a thing. If you get more than 10 results, you’ve got a golden opportunity.