Well besides that fact that there will be more origin characters, so we will most defnietly not abke to take them all ... wich was confrimmed both by datamining and Sven himself.
There is one tiny detail here: Long rests. Since right now story progression is tied to resting especialy with companions ... since we can talk to them mostly in camp only. If you add two other characters we could spend much more time in field ... since we would have more hp, dmg, spellslots, carry weight ... more everything to keep us from resting. 🤣 Personaly i dont see that as a such huge problem ... i say let people screw the game the way they want ... but since you asked. 😁
In the words of the senior NCO instructor at cadet battalion: “If you ain’t cheating you ain’t trying. And if you got caught you didn’t try hard enough!”