What level are you at in your French and Spanish? I'd say Russian would be a good idea if you have a very solid level in the first two (I know you'll be doing A2, but the level varies greatly). Otherwise it might be a good idea to pick something easier, as you don't want to end up spreading yourself too thin and ending up not speaking any of them that well, or focusing more on one or two and neglecting the others.
Have you tried Russian yet? As it's so difficult you'd need to be really motivated, especially if you're studying two other languages on top, and employability alone probably wouldn't be enough.
Final thing - have you thought about your year abroad? Languages are only really useful if you have a high level in them, and you'd definitely need to spend a great deal of time in Russia to get your Russian to the level it would need to be. I read on another thread from someone that spent her entire year abroad in Russia that those that only spent six months there struggled when they came back. But of course if you did spend your entire year in Russia then your French and Spanish would suffer.
Conclusion - Russian if you're really motivated, have a good level in the first two languages and are prepared to put in a lot of work in all three languages, as come final year you'll be competing with people that have spent a year or a good six months in the country. Otherwise, Italian would be a better bet. I would recommend trying a bit of Italian and Russian before deciding, as 'employable' and 'easy' aren't the best criteria.