[foodevl]

It's actually far easier than you're making it out to be, because you seem to be assuming an ideal voltage source. Most linear regulators can only source current, not sink it. So it is perfectly fine to simply put a LDO at both ends and tie them together. The bus voltage will be the higher of the two. No extra diodes needed, certainly no active monitoring, and no extra current will follow even if the regulators are putting out slightly different voltages. Maybe add a small series resistance to limit initial inrush current as capacitors balance, but that's it.

[simcop2387]

That's a really interesting and novel way to address it. It does leave a potential issue though, it could lead to double the current being available to a device in the middle which could mean it could overdraw for it's own specs and melt or start a fire. Unlikely though.

I'd also say that with an LDO, the LDO is providing the active monitoring since it'll need to monitor the output anyway in order to regulate properly. You'd definitely need a resistor following it, not as much to limit inrush or anything, but to prevent the two regulators from causing oscillations (one turns off because the voltage looks good, which causes the other to cycle too).