Here’s an example of what I achieved with Local Lab. It’s not perfect yet, but I think it’s usable most of time.
I used @Wocket’s photo from a PlayRaw contest.
Original photo (scaled down):
With a single large RT-Spot:
With additional “excluding” RT-spots on the pine tree canopy to protect it:
Decentered “vignette filter”:
One single (decentered, asymmetric) RT-Spot, set to “inverse” mode:
Is that what you expect to do, more or less?