I am renovation my 50s rancher. Houston Tx 

This started out to be a basic remodel, but then I started following GBA, JLC and FHB and got hooked, so this has now become a challenge, and return on investment is no longer a concern, our forever home. 

Currently converting to conditioned attic, new deck, R19 batt between rafters, 3/4″ plywood, grace I & W, polyiso R25 CI, 1×4 sleeper vent channel then top deck with shingle sys.  High performance .2 or better UF windows, Hi performance VRF AC / ERV / Dehumidifier / HP-WH.  Eventually I plan to do a serious upgrade to the original exterior walls, outsulation / rain-screen 

For the near future I am stuck with the existing wall configs, but will add secondary 2×3 wall to upgrade the insulation [ dense pack cellulose or fiberglass or OC spf ] opinions welcome.

The current config   exterior gypsum sheathing,  top half  horizontal 1×4 furring with vertical 1x redwood boards painted,  bottom  brick with 1+” air gap and no weep holes so no air flow, but able to dry both ways.  Bricks several coats of paint so probably no vapor drive effects. and virtually no air leakage except around the window sashes

After 70 years the GYP sheathing seems to be in excellent shape, . no water damage, and no mold. This wall is very well sealed due to multiple layers of paint and quality construction.
  

Also 2.5 foot overhangs, single storey.

So my question:

Since It’s not practical to install a wrb over the outside of the Gyp Rock at this time, would it be worth while to create weep holes at the bottom and figure out how to allow air to rise up past the horizontal furring or keep it air tight and hope for the best. I worry that opening up the wall, some of which have virtually no sun exposure, is inviting moisture accumulation in the Gyp Rock.

Also which way would I be better off, using cellulose between the studs which can work as a moisture storage buffer or fiberglass, counting on immediate moisture dissipation through the sheet rock walls.

Thanks Mike

PS: to open up the wall for air flow, I would cut out vertical 2″ strips from the gyp rock [wood part of wall] then cover them with a wider strip of gyp rock creating narrow 2″ by 1/2″  vertical channels behind the furring strips.