We already do. A lot of surnames were of a non Anglo-saxon origin (or should I say Celtic?!), and were spelled in a way that made sense to the British rather than the correct spelling ..can I think of any examples at the moment? Of course I can't!!!
Actually a good case in point is Irish Celtic names - have you seen how they are spelled? E.g. Niamh - spelled as Neve (e.g. Neve Campbell). I assume that is not to do with the international convention in phoenetics... I never have understood that:-)