Curation idea: should we be able to upvote off-chain content?

I've been thinking about "curation" on the blockchain since reading @remlaps post about it the other day. It seems to me that one of the big problems with userbase growth on the Steem blockchain is a network effect problem: if a content creator looks here and doesn't see people that are likely to upvote their stuff they aren't interested, and if someone who wants to use their assets to reward creators looks here and doesn't see people that they want to upvote then they aren't interested.

But there may be another way to think about this. Right now 50% of the rewards distribution goes to "curation", i.e. rewarding users for highlighting good content with their votes. Right now the only content you can get rewarded for curating is content that's posted to the blockchain because the only thing you can upvote are blockchain posts. But what if there was a way to upvote content that wasn't on the blockchain, say a YouTube video or a substack newsletter post? Currently the blockchain says that 50% of rewards are about curation, and you could make the argument that we should be able to distribute rewards to steemians for bringing good off-chain content to people's attention in the same way that they should be rewarded for bringing good steem content to people's attention. (Obviously the ideal is for lots of good content creators and supporters to all already be participating on the blockchain, but I don't think that's where we are right now).

A full-featured implementation of something like this could mirror posts from other platforms and hold the author rewards until the actual creator shows up to claim them, but there are a lot of thorny trust and IP issues there (e.g. How do you handle people who don't want their stuff on the blockchain? How do you confirm that someone who shows up to claim the rewards really is the creator? Who holds the rewards until the creator shows up?). But a halfway solution would be to be able to just post a link to the content and not distribute author rewards to it, just curation rewards to people who vote on the link. That sidesteps the ownership issues, and gives us a broader range of things to use our upvotes on.

I think a really robust implementation of the ability to upvote anything on the net might require some support at the blockchain level and/or in the condenser UI, but I think there are ways to proof-of-concept it without needing technical or business support from the Steemit team. What if someone created a website tool where you could just plug in a URL and it would then create a blockchain post from an account called something like "offchaincontentbot" that's just a stub with the URL and it would set the author beneficiary to "null". The person who wants to upvote the offchain post uses that site and then just upvotes the stub post (presumably after waiting a few minutes to pass the limit on too-early curation). I think this means that any curation rewards would work like normal, but no author rewards would go to the person who is just submitting the link since they aren't really the creator of the content (ideally the rewards wouldn't be thrown away, but since we can't get them to the actual author this seems like a good compromise, at least at the proof-of-concept stage).

There may be implications I haven't thought of yet, and it certainly has the potential to change the reward economy if people aren't focusing as much attention on steem posts, but it could also give more people reasons to use the chain which would be good for the long term. I first floated this idea in a comment on @remlaps post, but I thought a standalone post might get some more visibility and discussion. What do people think?