I don't get what your point is exactly... it wouldn't really make sense to take Na K and Mg in Iodide form, because you could take advantage and get, for instance, your required amount of other elements if you split them up and took (for example)
You could get all the Iodine you could possibly want from KI without really over-doing it on potassium.
KI is 75% Iodine and 25% potassium by weight, therefore you could take 20g for your daily potassium intake and end up with 15g of iodine... sufficient, if you ask me.