A good point Rob.
The option to stand must be considered from the position that no dispensation is allowed. At present a shooter would approach the Chief Marshal for permission to stand; hence dispensation. If no dispensation is allowed then it would mean those who cannot kneel would score zero if they were not offered the alternative to stand.
Now I can only hope for integrity in that a shooter that can kneel does so. We have talked endlessly about not being able to make a judgement about a person's physical ability so this rule would be if you cannot kneel then you can stand; it's your choice.
In mid-course can you change your mind. Under this rule yes, perhaps your knee/ankle is sore and you tried to kneel at the first lane and then thought better to stand.
Now if dispensation is allowed then we stay as we are: ask for the Chief's permission.