Modifed Rubs

Salt is cheap, spices are expensive. Therefore to sell you a big bottle of rub add lots of salt and few spices. Now days transportation and packaging are also a significant contribution to overall price of the product. Ingredients have to be listed in the order they are present in the mix, so the best way is probably to mix your own and only use the salt you want or salt separately. There is no easy way to remove the effect of salt except to add more spices, and therefore sort of dilute out the salt, which sort of defeats the whole purpose.

I guess any additions would depend on the paritcular rub and the spices that are dominant. If we're talking about a "typical" BBQ rub, then spanish paprika might work; not overpowering, and will add a depth of flavor.