Working in consulting I can certainly see your dilemma. We have often thought about billing like that, but ehrn we have compared our fee to the size of the clients business, the clients do not receive it very well. (Close to "Mind your own business!" to put it mildly).
By billing by the hour you stay on your own side of the fence and can motivate your costs, but you do not get a part of the value you create.
I have seen it presented by one consultant, and he ties his fee to the performance of the business (increase in revenue, bottom line) after he has been involved. But he is a big shot strategic consultant working strictly with coaching top management directly. On that level it could make sense, as your impact can be more directly measured.
I would consider one of the following options:
- If your impact can be very directly measured - f.ex. If you are involved in the launch of a new product, business area or similar - it could make sense for both you and the client as you can measure f.ex. revenue generated
- Try to package your deliveries into products or components, as they are more scalable and easier to charge by user, revenue or cash flow through your delivery. It can be hard in a lot of traditional consulting deliverables, but try to be creative about it. Software licenses have been priced like that for years. That way you do not have to justify the time you spend, so it is easier to charge the margin you are looking for.
- If you have no doubt about your value creation, go all in! No cure, no pay - if the value is not created, you do not get any money. Significant downside, but also upside. Again, you need to be able to measure your success correctly.
The good thing is, that you can experiment with this approach without harming your other business, as I assume you work with your clients individually.