I've had to drop your keyword for media-sound/sox-14.0.0 due to missing dep on ladspa-sdk via ladspa useflag. I don't know if you prefer masking ladpa useflag for sox or keywording ladspa-sdk.
Sorry for the inconvenience.
It's been few months with no response whatsoever from mips team. Masking the use flag, and if that's not enough dropping the old ebuilds in 30 days.
There is no more sox ebuilds in tree for mips.