Previous questions have asked if it is possible to turn compiled delegates into expression trees, for example:
Based on the response, I'm going to answer my question:
No.
Though of course if someone comes up with a better answer (or I come across one) I will update.
I did a library that supports .NET 3.5 expression trees:
https://github.com/ashmind/expressive
I tried to do internal API so that .NET 4.0 support would not be that hard to add.
You can add or change steps in the IPipeline implementation to achieve just that.
One thing that I haven't done and that will be hard is support for loops, though.