AVFS - Avisynth Virtual File System seems to bridge the gap pretty well.
http://turtlewar.org/avfs/
AVFS is a virtual file system that exposes the output of Avisynth scripts through the file system as a set of virtual media files. This allows Avisynth to feed media applications and converters that do not use the VFW API. It also allows accessing Avisynth script output through network shares, and allows mixed use of 32 bit and 64 bit video processing and consuming applications.
AVFS uses the Pismo File Mount Windows system extension. This extension enables user mode file system development on Windows.
You do need to use a cmd window to mount the avs script file for use by VLC. The AVS instructions are reasonably clear:
To mount an Avisynth AVS script, from a cmd.exe prompt run:
>avfs somescriptfile.avs