Richard started discussion about perfect passagemaker. It seems that it is interesting concept to a lot of people. Unfortunately, most of them will never have a money for such a boat. I think it could be interesting to explore possibilities to design something similar, on the budget, sacrificing some of the space and luxuries, but still retaining able voyaging power boat. (Auxiliary sails allowed).
She has to be cheap and easy to build, use and maintain, very fuel efficient. That means long, narrow hull with a sharp bow. Cruising speeds 4 – 8 knots.
Money can be saved by avoiding expensive nautical toys and luxuries, keeping everything simple, work-boat style. During a voyage, fuel could be saved by careful route planning, making use of favorable currents and winds and motoring at slower revs.
I think that sardine carrier or older generation life boat type of boat with simple, auxiliary sails would be appropriate for the task.
In the attachment, some of the boat shapes and rig that I consider pretty closely suitable for the task. (Of course, they have to be modified for cruising). What do you think?