I'll have to give it a closer look, but from a cursory look it seems that there's no avoidance of the bootstrap problem (given two chains, which one does a new node choose?), and no guaranteed Sybil-resistance in the "honest majority" required to avoid the grinding attack.

It would take the endorsement of someone that I consider extremely trustworthy to even go to the trouble of trying to deconstruct whether this approach is valid.

It stands, I think, in stark contrast to the simplicity of the proof-of-work based Sybil resistance, and the "central authority will sign the block" based Sybil resistance.

That said, given this discussion about the nature of trust, this scheme may work in effect, even if in the end it devolves into a centralized or social proof to find the correct chain. I'm not sure it adds a lot on top of that except instilling some potentially false sense of security in naively written nodes.

It requires a majority of trustworthy nodes to be online - it cannot deal with a force majeure, such as a massive power cut.

What can though? If a large fraction of Bitcoin miners went down you'd need less hash rate to double spend.