The missing link I never knew that OJ futures as a trading commodity existed, I thought it was just a consumable product. Anyway I would say that morddwyd should rest easy and carry on with vodka & orange, vodka's horrid with tonic, that only works with gin. A few drop of Angostura bitters in either with the OJ improves both no end.
I seem to recall when Florida in the good ol' USA had a disaster with their citrus fruit harvesting, and how that was going to effect the world. Surprising how the same commodity can be sourced elsewhere, and a few can make large profits on a scare rumour?.
Providing extra additives to Vodka, is like adding extra water to whisky (whiskey) ;o)
But vodka like gin is a fairly flavour neutral cocktail spirit, awful on it's own, but takes a very flavour neutral part in making an excellent cocktail with any other flavours taking the primary flavour, as Gordon's Gin claim on their labels the heart of a good cocktail.
Whiskey, brandy, whisky or bourbon are powerfully full flavoured spirits that retain their base flavour whatever you put in them, even when drowned in mixer!
As for shouldn't mix anything with a spirit, everyone to their own. I can't drink any spirit neat anymore without getting instant heartburn, so I don't. A little ice or soda is now my choice to tame malt.