Should people have an alternative way of being rewarded with merits besides posting?
How could this look like, and how would you design the system so it can't be abused?
No, the situation is already bad as it is. There is no reason to make it worse. There are plenty of merit sources that give out merits for low quality posts, you just need to post in the right threads and in the right way. Quantity helps people who post lower quality posts. If you create extremely high quality posts or contributions you are going to do better for much fewer posts though.