SO ANYWAY back on topic... ((BTW There were female humans made into Koloss, though I do not know if that translated into having female koloss))
I thought about this the other day too. I don't want to spoil anything, so lets just assume Kandra CAN match the DNA of the flesh they replicate. (the flesh they make is a perfect copy) Melaan could become any woman, and have that woman's baby with Wayne. She would have to learn to carry it in a womb though, learn how to make amniotic fluid, how to eat food for it, give it oxygenated blood, carry away waste... more work and research than has probably been done. And in the end who knows how the SDNA thing would work out; tied to the human mothers? or to the surrogates who carried the baby? (Melaan)
What I personally think is most likely, IF a half Kandra is possible, is that it would be born a little baby mist-wraith BUT wasn't so blocked cognitively. Basically it would grow up, slowly learning to use bones and copy it parents. You would end up with a Kandra that didn't need spikes but wasn't immortal and could also breed true.
I like to imagine that kandra human hybrids are actually the future of the species. Though since Kandra themselves can't breed (and thus can't even copy however mist-wraiths do it) I imagine this would require Era 4 science.
I wonder; If Milaan took her spikes out, could she temporarily breed then? HOW do mistwraiths do it? That seems important...
[Edit] Goofy (and 'adorable') mental image of a little translucent pile of gooey muscle rolling around the floor making a 'skeleton' from baby toys like wooden blocks and plastic car keys, and Wayne is just grinning like any normal glowing parent watching a crawling baby, seemingly obvious to the oddity of the situation.
Meanwhile while Melaan makes an off-handed remark about the time Wayne left his dueling canes out and the baby broke his shins before giving them up.
"It would have been easier for you to get them back from her..." -Wayne
"My shins are an heirloom, and yours are much easier to repair!" -Melaan