Baldric for a late roman spatha?

[XorX]

I think this is quite what Thomas meant in his second sketch. It would make sense when the knotted ends of the sword belt are clamped under the broad belt (between belt and body). So they would not be visible and the whole system be fixed better. The sword would hang a bit deeper than in your drawing ( like high-medieval scabbards).
The whole system makes more sense than the "official" reconstruction, I think.