General Achievements that give Credit rewards are currently planned. They may not be included in the initial roll-out of the LB Update, but they are definitely a feature that the Devs plan to implement. In fact, you can get Credits and an Achievement right now by completing the tutorial in the hub.
That being said, the idea to incorporate Credits gain or loss into gameplay is definitely not going to be implemented. We use the points system and bountying for that reason, and we prefer to keep it like that because no money is involved; it's all gameplay-centered. If we swapped it so that Credits took the place of points, I can see a large uptick of boosting (since now there's a real-money incentive to do so) and Pay to Win (since people who buy more Credits can put higher bounties or sponsor the best stuff to win), and a decrease in the purchase of Credits packages themselves (for people who would rather just grind or boost than shell out money). There's just too many risks with too little benefit, and we can achieve the same benefits with alternative means.