In general companies will not want to start paying in a foreign currency or have adjustment provisions that would put risk on them (and you, actually as they may decide to cut you loose if you suddenly become more expensive).
This is a common problem for people paid in foreign currency. They can win or they can lose... Not many things to do apart from negotiating a salary high enough to make it worthwhile or to play the currency market (i.e. don't immediately exchange what you don't need to if you think exchange rate will improve).
I suppose someone would only consider that arrangement (being paid in a foreign currency as a remote contractor) if that was much better paid than local salary in the first place.
