While we are told explicitly what Wallace's motivations are (by Wallace himself, no less) for me it doesn't add up with his actions.
In the movie we are shown and told by Wallace himself that he has a God complex and wants humanity to conquer the whole universe.
In his eyes to achieve that would require a slave force of Replicants, alas "I can only make so many". That's why he wants to find the key to the question of Replicants reproducing (which he believes Tyrell had found, but had taken it to his grave), so that the slaves can reproduce themselves.
At the same time though:
he disposes of a newly born Replicant right away, without bothering to utilize her in any other way, just as soon as he recognizes her as barren. If you "could only make so many", why disregard them with such ease?
the current generation of Replicants (Nexus 9? I don't think their designation is specified at any point, but I mean the type K belongs to, the seemingly obedient ones Wallace introduced in 2036) are supposed to not develop emotions or at least be able to disconnect from them (hence the nature of Baseline test). And yet he expects Replicants to reproduce themselves in order to inhabit the universe. How are they supposed to connect and make babies without emotions?
That's why I think Wallace's motivation makes no sense.
My theory is: could Wallace himself be a Replicant? Could he be a clone of an actual Wallace that once existed, with his God complex and vision of colonizing the Universe, but the Wallace Replicant - knowing what he is - is actually more interested in solving the riddle of Replicant reproduction, because he finds himself and his kin lacking compared to humans?
'Only make so many'isn't really that little, he says he has "millions [of children]"; so disposing of one, isn't a very big loss.