[...] Rewards for kills would just kill the support classes and lead to the aforementioned peasant hunt. Why punish all the close ranged support and stabby polearm guys who cause the enemy to drop his block only for the tincan with the big weapon to steal the kill. In the same vein, why reward all the tincan spammers who are out hunting kills while their team desperately struggles to survive/protect the flag/whatever. [...]
You say that it will only cause a hunt for kills and we should not reward spammer, but how do you think we win a battle (battle mode)? Spammers are already spamming like crazies to have a good multiplayer, they want to win that for sure.
In Siege, they might go hunt kills and leave the flag alone, that's why I think the multiplayer should still be the best way to gain xp/gold (#1) and then add xp/gold for kills (#2). If you killed a lot of players, you indirectly helped your team: if you are dead, you cannot go capture the flag.