Non-Mammal Mammaries: Averted, except in the highly specialized case of bioshells (emulating species in which one sex or another has, ah, notable mammary glands) built for infomorphs who prefer their sexual characteristics to match their gender-emulating code.
Assuming you don’t make the point that mammalianism is a trait that goes with the body, whatever the mind that’s in it, anyway, which is probably a more valid way to look at things in the first place.
Half Human Hybrid: Even generalizing this to allow for the lack of humans in the known part of this universe, and even taking into account the amount of xenosexuality going on (refer back to Boldly Coming and Interspecies Romance) – no. Just no. There are absolutely no half-anything anythings wandering around, because these aren’t just different species, they are the fruit of entirely different evolutionary trees. Ain’t going to happen.
If a mixed-species couple really wanted to have children this way, yes, in theory, they could spend millions of currency-units on paying for the design of an entirely new neogenic species incorporating features of both of theirs – but, of course, the child would then be a unique member of a completely new species. Unsurprisingly, this is not exactly a popular option. Instead, most of them just have (through technological assistance) children of one or both of their own species, with the option of engineering in some parallels of the traits of the non-matching parent, contributing genes through memes, as it were.