If I was a bastard who wanted value for money, I'd hire those part-time mums. From what I've seen, they end up feeling obliged to work out of hours, so you'd effectively get 0.8 FTE while paying for 0.4-0.6. Roles like social media or content writing with scheduling involved instantly creeps into days off. Horrible approach from an employer, but like I said, if I was a bastard.