Companion builds?

So I've read a lot of threads about companion likes/dislikes, and all of them say to plan out your party before you start, but I've so far found no threads about which ones are best for what.
Any ideas? I know Aleifr is a trader, Orosio and Ultan are medics, Agasicles is an engineer and the rest, unless proven otherwise, are just infantrymen you can give custom equipment.

Infantry men, or Heavy Cavalry...