pattern modifications:
cable cast on.
after ribbing, k first stitch of row together with last stitch of previous row (eliminates a purl column for symmetry on either side of the chart), did not switch to stockinette; kept twisted rib outside of the chart.
Twists in chart are with knit stitches; I decided to twist them.
chart A row 2 and 12: left twist, no purl by: knit into back of second of second stitch on left needle, knit into back of first stitch on left needle, slip two stitches from left needle.
row 18: no purls in center twists
row 19: twist the center knit stitches.
reduce needle size after chart A from 2.75mm to 2.5mm.

do not decrease stitches; change in needle size creates the shape instead.
chart B:
row 1, 7, 17, 22: first twist left with no purl stitch
row 6, 20, 24: twist the center knit stitches
row 19: no purl in twists
row 23: no purls in center twists

on first repeat of chart B, reduce needle size after row 16 to 2.25mm
on the second repeat of chart B, reduce needle size after row 16 to 2mm

GAH! I finished the left armwarmer only to catch some skipped rows in working the following. So, the following is still being worked out while I rip out and rework it:
on fourth repeat of chart B, increase needle size to 2.25mm; begin thumb gusset from 7th stitch to 11th st from the chart (to the left or right, depending on the lefthand or righthand arm warmer) immediately on beginning 4th repeat. Work thumb gusset in twisted rib, keep palm in ribbing. On the 23th row of chart B there should be 17 stitches in the thumb gusset. Stop increasing and maintain ribbing until end of chart B. On last row, work to gusset, put stitches on a holder, cable cast on 1 stitch, finish row.

chart C: purl stitches instead of twisting them on row 16 (there were no twist stitches on the corresponding row in chart B, this change is to match previous chart.)

first row after chart C, p1 k2tog, knit across chart sts, finish row in ribbing. Then rib until bind off, 1”.
Thumb: pick up 7 sts, rib 1”.