Rather than adding another currency in terms of tradeable fuel, why not just drop premium boxes that give only fuel in a fixed amount? That would allow you to sell the same premium cards as before and also control how much fixed tradeable fuel there was using the boxes. If you wanted, you could also sell more boxes seperately.
If you allow people to buy trade - fuel directly you create an alternate currency system competing with the premium and L3 keys people have been using since the game started. It's going to end up devaluing the keys people have already accumulated. Prems and Keys give highly variable rewards. If you compare that to a fixed value currency, the interest in prem cards is going to crash. I know, for example, if I had a choice of buying prem cards or fuel as a trade currency, I'd never buy another prem card and likely would never accept one in trade or use them ever again.
It seems like a great way to anger anyone that has been spending money in prems or trading in them.
It's not like the Christmas box drops. I farmed those hard and there was still a reasonably low absolute limit to the number you could find in a month. Plus the amount of fuel in them was pretty small and trading them in groups cost a significant amount both ways. As a result, I bought some fuel but not a lot. Even then, it was pretty clear that a handful of boxes with a fixed amount of fuel were far more valuable to people than a key.
You're completely right. Unless the rewards that back keys are improved, it would be far more rewarding to buy fuel than to buy a premium key and open a premium box. Either CAG should back premium keys more strongly or make these fuel packs very expensive relative to non-tradable fuel prices. While I do support the idea of buying tradable fuel packs from the store, it could easily throw the economy of balance if it's implemented without care.
Now, a question for CAG, how do you plan on introducing a new currency without rendering the current currency of keys obsolete?