I think the ME companies should simply match the erosion of their currency compared to world markets. They themselves do it nicely with the increase in oil price.
They can adopt a ERP (and i mean a FULL ERP) for every expat in his selected currency. This would work up OR down, which might even be cheaper in the long run. Or they should compensate for inflation of the local currency, as they do for the locals.
Not doing either, especially when only compensating locals, is discriminatory (or even racist) and is rightfully bashed. They are very quick in denouncing similar practices if they are victims of such abroad!
I don't mind if they give locals a piece of land, or if they have a national pension scheme for them. This is looking after their people and is basically outside of the respective company. However concerning salary and T&Cs it should be the same for every fellow worker irrespective of nationality, or you create a double standard which in our business is detrimental to motivation and safety.