It's never been particularly successful in the past, and bearing in mind any competent coder could do a fit for purpose, easily maintained turnkey alternative, may be you should look at your sales pitch. You don't have to gamble on whether the developer is competent !
I wouldn't recommend a solution like this to anyone. I know I could do a better fit, I know it would be a lot more efficient because it was a better fit and I know I could tune the better fit to the clients needs.
The more modular, adaptable and configurable you make the system, the more complex it becomes. So you either end up with frontpage themes or C++, strike a happy medium you get the best points of neither and the worst of both.
PS I'm not comparing it to frontpage, that was just a similar member of the genre I literally plucked out of the air. I'm sure the stuff you are trying to sell is much better than that.
LOL