Instead of this modding laws so they increase levy size as they increase retinues would be possible as well.
Many Islamic Sultanate had standing armies whose members were mostly former slaves or POWs. Ottomans even started Janissaries like that then made 1/5th of christian son of each family a janissary. In my opinion mamelukes, ghilmans, varangians etc. should not be represented as mercenaries but a new type of cultural retinue with lower cost in exact contrast to like cataphracts - although a cultural retinue quite expensive to build and consumes too much retinue points.
Many Islamic Sultanate had standing armies whose members were mostly former slaves or POWs. Ottomans even started Janissaries like that then made 1/5th of christian son of each family a janissary. In my opinion mamelukes, ghilmans, varangians etc. should not be represented as mercenaries but a new type of cultural retinue with lower cost in exact contrast to like cataphracts - although a cultural retinue quite expensive to build and consumes too much retinue points.