License them the idea. Retain ownership. Did they flat out SAY "Yes, we want this; if only we or someone else would develop it?" You can hire support teams, you know. I wonder if you are letting a few shadow issues stand in the way of a good order.
great questions - we see this situation with our clients pretty frequently at my firm. based on my own years of SaaS/tech sales, marketing and project management experience, I would say the path most likely to get adoption is actually discovered before the demo is delivered, rather than after. ...