PS does anyone know if that might actually work (ignoring the fact that such rings don’t exist)?
for 31T wouldnt you need an overall chain length that was a multiple of 15 (paired) links long and have the requisite number of halflinks in just the right spots to make up the full length.
depending on your halflink design you get ..nwnwNNwnwn.. so line up your half links with the right spot on your matching 31T ring and off you go.
doable – I think – but probably not worth the bother, too slack or too tight a chain length, having to mount the chain exactly right when you do wheel changes, too much of a PITA, plus dunno what the half links would do to chain retention.