I just submitted a proposal, selling "design solutions" rather than hours. Funny/strange/sad how designers of all stripes will undervalue their work, or be susceptible to others devaluing their work. I didn't fall into this scheme, this time. Broke out the project into four phases with 'a la carte' pricing, but made sure that the first two phases were more or less mandatory in order to get the project completed. The last phase was CAD which would be estimated and budgeted on an hourly basis rather than a lump sum. As a manager now I have direct insight into how long projects take even the most efficient designers, and the sad truth is that a lot of freelancers are making very little compared to where they should be.
However - we shall see what the potential client says in return. In which case, the lunchbreath graphic rule shall apply: