Yes, it is available in all current builds.
Just define (for each armor), which soldier types are allowed to use it (attribute "units").
E.g.
armors:
- type: STR_MY_SPECIAL_ARMOR
units:
- STR_SOLDIER_TYPE_A
- STR_SOLDIER_TYPE_B
soldiers:
- type: STR_SOLDIER_TYPE_A
requires:
- STR_TECH_TO_UNLOCK_SOLDER_TYPE_A