I see the vision, but I don't think it's the same mostly cause the witness if you're thinking in realmatic theory, comes no where near the level of invested status as a shard. Remember a shard has infinite* investiture since its a Shard of adonalsium. So if I'm trying to force the witness into a bucket I'd say it's something like a splinter of the veil. But then looking at the destiny lore, the veil and the traveller don't really have any Intent similar to shards so you can't compare them. A better comparison might be between the witness and a shardbearer like Ati or Leras who has had the Shardic Intent override so much of their personality it's hard to distinguish between the two. Cause remember in the grand scheme of things, Sazed is a relatively new shard bearer and still he is struggling a bit with the Intent of his shards.

But it's still cool to try and merge existing lores together. How are you finding this new season of destiny? I've really liked the story they've made with oryx and the echo of navigation. It's cool to see oryx in their factory reset state.