Did you take a look at the filter system? Because it pretty much does exactly what you want
Yeah your outline pass should be a Filter. You are reinventing the wheel here.
Look at SSAOFilter, CartoonEdgeFIlter, and BloomFilter.
All theses filters are rendering pre render or post render passes, see how it’s done.
The FilterPostPorcessor allow you to stack multiple filters.
Thanks s lot, I will take a look at Filter System, it’s good to hear that there is a solution already.