I agree with Konrad's opinion on this matter.
I think the best solution is a clarification that states:
If a player declares that one or more of his companies will move to a site already in play, he must verbally declare which site each of those companies will attempt movement to. Alternatively, he may write down on a piece of paper which site each company will attempt movement to, and thereafter show this written declaration to opponent at the beginning of said company's Movement Hazard phase.
The above clarification would prevent any retroactive mind changing based on what has occurred in the game between the initial declaration of sites and the time a given company's M/H phase begins. This would also prevent any chance of an unfair situation where one player sticks with his "mental" declarations while the other player does not.
If, however, the above clarification is not deemed a popular choice, I would still prefer the proposal by Jose-san and Bandobras rather than making no clarification at all, and thus leaving the situation and how to approach it unclear.