What if source skills could be designed in a way to allow for optional source point usage?
So, for example, what if chain lightning was the source-infused version of electric discharge? At it's normal form it has normal effects, but you can optionally pour source into your casting to make it devastating.
One advantage is that you don't feel like you're wasting your memory points by having a source skill memorized, since the base skill is useful when you're not investing source. To counteract this, maybe make spells that cost have a source version take up more memory? Or even have a single "infuse with source" skill that takes up one memory and can be used to... well... infuse with source. Cast it on yourself to make your next "sourcable" skill be its source version, or cast it on an object to do the source things that you sometimes spend a source point on out of combat, or even cast it on an ally to donate a source point.
Maybe you can even cast it on the ground, to create your own source puddle, or make something on the ground erupt into an explosion of magical energy, like fire damage to everything in a flames zone or poison damage to everyone in a poison zone.
Lots of possibilities, I think.
