Dark dyes usually do contain a low volume developer anyway. I can't see any benefit to hair health in going darker gradually, you are just repeatedly exposing your hair and scalp to harsh and damaging alkaline chemicals.

Lifting is somewhat different to going dark. Lighter you are removing the melanin pigment and blowing holes in the structure of the hair, so damaging both cuticle and cortex. Darker you are adding not subtracting pigments so mainly concerned about damage to the cuticle.
2a-2c, medium texture, porous/ colour treated. Three years CG. Past bra strap length heading for waist.

CO-wash: Inecto coconut/ Elvive Volume Collagen
Treatments: Komaza Care Matani, coconut/ sweet almond/ fractionated coconut oils, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss Ultimate Volume, various Elvive
Styler: Umberto Giannini jelly, Au Naturale styling gelee
Flour sack towel, pixie diffuse or air dry.
Experimenting with: benign neglect