Multi-circuit splice aesthetic issue
Per Mom Orders, I recently removed an 6' wide dividing wall between her dining & living rooms. The late wall contained hardware for three circuits, and seemed to be the approx. midpoint for each. The issue I have is how to aesthetically splice two circuits that were on opposite sides of the wall (one switch, one outlet) and can't reach each other to be spliced in one 2-gang box:
Ckt #15 (removed receptacle)
LR receptacles, mid-run. Enters through corner stud 10" high. Exits through ceiling
Ckt #21 (removed light switch)
DR receptacles and utility light, mid-run. Enters through DR wall ~42" high, exits through ceiling.
All this occurs in the 2' wide stub wall where DR met LR. (LR is 2' wider than DR, so imagine that junction) I wanted to just splice both circuits in a nice 2-gang box with a nice blank cover. Unfortunately the previous homeowner was an idiot, so there's *zero* slack in one wire on both circuits; i.e. #15's ingress is only long enough to reach the removed receptacle, and #21's egress is only long enough to reach the removed light switch.
So, that means two splices and two boxes. However, since the wall is gone, that'd mean one blank plate at ~17" and another one above it at the odd height of 40", which is unacceptable to The Boss.
I can't just terminate the lines, because each is mid-run and services a half-dozen receptacles. Also, due to the hell that is loose-fill celluose in the attic and other impediments, it's not possible to replace the short leg from each circuit with a longer wire.
The only thing I could think of was to splice #21 at switch height, and run #15 through the floor and J-box it to a joist from the basement. It's my understanding that splices have to be accessible, and that would accomplish that.
But I thought I'd ask anyway; Is there a better solution? Lots of poring through NEC & NC's code reqs hasn't given me much help, so I'm left with little choice but to appeal to the old work masters here to share from their huge bags of tricks :)
Thanks in advance!