Regarding Lizzie being protected -- perhaps
Durai or
Scratch is just really into long-term planning. Raising a child would be a big drain on resources, but maybe the relative safety of
the Colony makes it seem possible. It would probably take at least ten or twelve years for such an investment to pan out for Durai/Scratch -- but if they want to survive long-term, they are going to need new fighters/workers to replace the ones they lose. They are definitely ruthless enough to use child soldiers / slaves.
I'm really not sure about this idea though -- the theory that Lizzie and the baby are being kept as bargaining chips is probably more likely.
The Mallers' increased security at the Colony is the only reason why I think D/S might be considering the far future potential of Lizzie's baby.