Regardless I think you're really onto something that people want. There's going to be a trade off one way or another, but the Redis community is all about speed, so the faster and more efficient you can do it, the better (:
In a relational database this isn't normally a big deal, because the structures themselves (rows and indexes) are already versioned, and most rows are of a relatively-small size. So rows typically work well for intent/write-ahead logs, old/new version logs, etc. But with Redis, operations aren't just on a "row", it's on a structure, and that structure can be gigabytes in size (I had a 30 gigabyte ZSET about 4 1/2 years ago, that was no fun during snapshotting, let me tell you).