The signal is the problem in the first place. Holding the phone in a specific position blocks the frequency's path to the antenna. Using software to switch (or not) signals shouldn't improve the reception all that much if at all. The only way to do that would be to switch to a band (like microwaves) that isn't impeded by someones hand. (obviously not an option)
Granted higher frequencies are more susceptible to frequency blockage, but mobile frequencies are also very susceptible to blockage also.
It is handled in most mobile phone by placing the antenna away from were the phone is held (read top) since a hand usually wraps around the phone blocking several different directions. Blocking a signal in one direction is okay since mobile towers usually exist in several directions with overlapping coverage. Software does allow that, but if a signal can't get through, software isn't going to fix that.
Obviously, I don't know the full story behind what is happening, but thus far it sounds more like a design flaw than a software issue. I find it laughable that Apple blames it's users rather than accepting blame for an obvious misstep.