A solution to Solutions.
We don't want to price you out of updating or using the solutions in general, so it is in both of our best interests to come up with something that makes sense.
Freeze the current solutions at the current level with the new EULA to protect your interests.
Change from solution packs of code, to solution generating extensions protected by the current system of activation codes. Everyone has to make some modifications to the solutions anyway, so create a simplified wizard that collects the information and options unique to the domain and spits out the code needed. Offer an upgrade to the full version of the extension to those that want more.
This would give you full control of the solution, give the developer the same advantages of any other extension, and make it simpler for the less experienced to get up and running quickly.