IMO you are born with the same amount of availablbe pronation that you die with....it is in the gene pool, now some people will suffer symptoms or have problems, others will be pain/ problem free for life. Now the fact the human foot was designed to walk barefoot on soft uneven terrain and we put it into flat shoes and walk all day on flat surfaces makes excessive pronation a bit like a repetative strain injury [the foot is constantly trying to adapt to the flat ground]
now to throw a spanner in the argument........ if your ABductor muscles are weak and the ADductors are tight then this will pull the knee inwards which will increase the effect of the pronation, strengthen the ABductors and stretch the ADductors and you can help the knee to track better and thus remove some of the visible pronation.
orthotics are best describled to be like reading glasses, they meake your feet FUNCTION better they do not make your feet better, they can/do however reduce the stresses on the various muscles of the foot and this can help recovery from injuries.
on the other side of the coin there is a 'system' called feldenchist [sp] which aimes to take the body back to the state it was on leaving the womb , before we inflict it to gravity?????
hope this all makes sense , i am never good at puting this stuff in writing