Changing AVC Metadata Without Re-encoding

Is there a way to change the metadata of an AVC elementary stream without re-encoding? For example, it would be useful to be able to slow down a 25p stream encoded with PAFF/MBAFF and flag it as progressive. Of course, eac3to can accomplish the slowdown, but the stream still reads as interlaced. (Changing AR would be another potential use.)

In short, it would be nice to have something that does for AVC what Restream did for MPEG-2. Is this possible? I tried searching for a tool to accomplish this but drew a blank.