Even if you took the current moderators, and used them to sort of define a moderation standard, you'd still be introducing centralisation there, since users would have to opt in on who they trust to moderate, the majority would pick who's the most popular out of them, retrospective to their actual moderation work.

Basically, for it to work you'd need a ton of statistics, a transparent way of showing what was moderated, and why, and then you can't bring in the current moderators as moderators for the decentralised forum, since that's introducing centralisation to a decentralised system, even if you get to choose who to follow for moderation.

Also, I think selecting multiple moderators to follow, and then seeing or not seeing content based on that would be confusing for everyone. Most new users struggle with the layout, and functionality of Simple Machines forums since they aren't used to it, let alone a system which would be confusing even for the most senior of users of that system.