Obviously the one doing the impregnating is the masculine partner and thus patrilineal names have no issue. Its' not weird at all. Did I spurt something into you and make you walk around like a goof with a bloated belly for a few weeks to months? If yes, I get to name it. Eggs, babies, doesn't matter.This also doesnt work. LT does not have a straight forward binary view of gender. Depending on how you set spawns and how you set masculine/feminine rates, a patriarchal way of inheriting last names mechanical wise (let alone lore wise given how matriarchal this game's universe is) simply doesnt work. Idk how children inherit names in the game and it kinda feels random but maybe there is an actually explanation and I just simply don't know how it works. But what I do know is that you wouldn't be able to do it based on gender (from randomly generated npcs anyway). Say if you set the game to where the game is allowed to spawn cuntboys and futas and a futa fucks a cuntboy, does the child inherit the cuntboy's name because he's a "male" despite the one giving birth or do they inherit the futa's name because they're the sire? Then you got the dolls who have no genitals but an asshole and have eggs implanted into them, who's name does the child take? the egg carrier or the one who planted it? See how weird this gets?
You can already make bovine taurs. Idk where you see that regular centaur's are the milky race. Sure, bovine taurs arent an "official" race per say, but im pretty sure the regular bovines already fill the role you're looking for.
In regards to eggs specifically, the child takes the name of the one who fertilized the egg, as the egg layer is still the feminine position. That means the doll that gets eggflated is double feminine, or superfeminine.