Not recommended — #25 of 31 Lyocell ranks #25 of 31 fabrics for warmth without weight. It is a poor fabric for this. Ranked on warmth relative to weight, with a packability bonus. The top pick is Cashmere.
Lyocell measures 75/100 for breathability, 13% moisture regain, 25/100 warmth, at 155 gsm. Warmth-to-weight is the metric: 25/100 warmth at 155 gsm is unremarkable for packable insulation.