This input plugin looks pretty much identical to the existing one except that you can add a 'luascript' setting.

YOu describe this as helping you offload processing, which to me sounds weird given logstash is supposed to be your processing system. Further, given logstash is capable of using multiple threads (and cpu cores) and redis is single-threaded [1], it seems like offloading any computation to redis would slow you down.

1: http://redis.io/topics/latency - "Single threaded nature of Redis"