Instead of karma, why don't you just implement 'good and evil' types of source points. Where doing 'positive karma' source gather activities would award good source points, which would be used to power 'good source' skills. And doing 'negative karma' source gathering activities would award bad/evil source points, which would be used to power 'bad/evil source' skills?
I think it would quickly lead to simplification - 'Good / Evil' Source and it shouldn't. The Source should stay as a completely neutral force.
