You are right that Steem is struggling with being splintered into many different ideologies and that it is harming the system. I hate the idea of the reward pool going away, but after quite a bit of meditation on the subject, it is likely the thing to do.
However, there is a caveat. The issue is that by removing the POB system for STEEM and passing it down the line to SMTs we are actually admitting that POB isn't working while not saying it out loud. Would POB on SMTs work? In most cases, probably not.
I have thought about this a lot and I would like to see POB work, but there is a hitch. The main challenge is that people keep using POB as a weapon against people they disagree with.
It really comes down to this, we all want a decentralized protocol, but all of us have something we dislike and do not want happening on that protocol. It could be spam, porn, circle-jerking, self-voting or something less anticipated.
So, thus we have downvotes and not just upvotes. There are legitimate reasons for downvotes/flags, but then follows ideological warfare, bullying and censorship/demonetization issues. "That one guy supports Trump and I just so happen to have way more SP than him, so lets auto-flag trail the motha-..."
Will SMTs really solve that?
Hold the fucking phone... So, we're going to solve this with SMTs? Okay, but that's not going to solve it. If an SMT decides to make their token not have downvotes then we run into the same issue of no enforcement against bad shit, or some dude buying a shit ton of the token and upvoting himself 10 times a day for posting "stake preservation post" or something stupid like that.
On the other hand, even with niche topics if downvoting exists for an SMT we'll run into the same problems. Sure, you can find more like-minded people with a more narrow topic, but that does not mean that everyone on that topic shares the same ideological viewpoints, and if they do not agree the downvote feature can fuel ideological warfare and silo mentality that breeds extremism.
For example, let's say a Christian community decides to create Christoken, the token that rewards people for praising the Lord! Sounds like a nice idea to begin with, but wait... There are a lot of Christian denominations! They pretty much all disagree with each other on some kind of ideological stance, and are angry at the other group over that difference.
In Closing...
The lack of a downvote button leads to an uncontrollable situation, and the existence of a downvote button leads to the encouragement of narrow thinking and the oppression of dissenting opinions. Fixing Steem's problems by pushing those problems onto SMTs is not a fix at all. POB is in trouble, and we need to recognize that and deal with it head on.
RE: One Currency To Unite Them All