Hi,
1.To grab the layer result after some of the effects are applied, you could make a plugin that you apply to your layer right after the last wanted effect. The plugin can grab the result and send it to another plugin (see communication between plugins...)
2.Same principle, but this time, I would add an adjustment layer right above the desired layer, and have a similar plugin grabbing the result and sending it where you need it.
But be careful with this kind of jobs: you'll have to deal with render order, image caching... On the paper, it works just fine, but in reality, you'll have to force render to fight AE's caching system. It's doable, but it's a lot of work, so, make sure what you want to achieve is worth it...
Cheers,
François