This is a contentious topic as there has been much debate whether a stiffer sole contributes to the pressure on the metatarsal nerves and joint tissue. A study in 2003 found carbon-soled shoes resulted in an average increase in forefoot pressure of 18 percent over more traditional plastic shoes. This makes sense. For example, if the sole is stiff, it won't flex under foot pressure and spread the load to other parts of the foot (imagine the difference between standing on concrete versus standing on a soft mat). However, some people swear that stiffer soles have solved their hot foot issues.
My opinion is this: If the pressure is across the entire ball of the foot then a stiffer sole probably won't help much and perhaps the sufferer should try a more flexible sole which, although less efficient, will flex a little more and spread the load over more of the base of the foot rather than just the ball. However if the pain is centered on a 'hot spot' then this could suggest that a stiffer sole may help with such pain, which could be the result of the pedal causing pressure in one localized spot.