I understand your thought process, and I agree that giving points to the poster of the idea would be a good way to reward the poster. Still the current scoring makes sense and should not be removed, just add another scoring. So you have my vote.

It happens once or twice a year that a community member posts a lot of ideas, most of the time halve of them will be merged by moderators like me, as they are many times previously posted ideas (and those points go to the poster of the original idea after merge).

Yep! The idea is just to make sure better ideas award more points