Kaidan's biotics are better than Wrex's biotics for crowd control (Lift + Throw on Kaidan versus just Lift on Wrex). Plus Kaidan has Neural Shock for some extra crowd control.
Typically, ME1 wants you to have a balanced squad (equal biotics + tech + combat), but after a few recent playthroughs, I am finding that the more biotics the merrier, so Kaidan + Liara as squadmates regardless of my own class is preferable. I even have a Sentinel right now and I use Kaidan and Liara and it is just Lift Lift Lift between the three of us.
Even as an Engineer, you will likely invest in Electronics and Decryption early so you can unlock everything yourself. This will allow you to invest points in Kaidan's Throw and First Aid early so you can unlock Lift and Neural Shock as soon as possible. Good for dealing with the Krogan Battlemaster on Therum.
As far as combat talents go, the only ones worth mentioning on squadmates are immunity and possibly Adrenaline Burst, although Adrenaline Burst is kind of wasted on Ashley. Both Wrex and Ashley can tank, but it takes a while before they can do it reliably. All squadmates cannot shoot very well; they always hit everything but the enemy; typically a box or your back.
Squadmates are more useful for crowd control, especially biotics (not so much tech) so Kaidan and Liara together are good.