IME, breeding good crosses is even harder than breeding good purebreds. You'd better know what the recessive genes in each parent are! I've seen full siblings in both Andy x Arab and Fresian x Arab that were as different as night and day.

Fresian x Saddlebred has interesting possibilities for creating a showy, snorty horse with action. I'd be really careful about a fresian x draft cross, especially if you want to ride the result. I think it would be pretty easy to end up with a "plow horse", in the non-complimentary use of the term.