I doubt it. Other than killing Gale which has a logical consequence, you can pretty much murder everyone without any "punishment." In fact often times the game rewards you in a way. Killing SH brings the artifact to you. Killing Lae with the tieflings is a solution to that encounter. Killing Wyll can be part of the gobbo path. Killing Astarion is justified by him putting a knife to your throat. And to "future" origin companions, Killing Karlach is also a solution to her quest which can be the easier option for some. Heck, each (current) origin companion also drops a rez scroll and potion which is super convenient. I don't think Larian has any Scruples about us murdering their custom characters. Heck, DOS2 was very similar and it was rewarding to "take care of your competition" as it were and kill the extra 2+ companions before they get murdered anyways.
tldr/ I think larian is totally fine with us murdering their custom characters.
That said, going back to main topic of party size, if they really wanted us to experience their characters, then a larger party size would ensure that those who want to can experience more of the characters. And even more so, they should not pull a DOS2 situation cause that'll be worse than a player choosing to kill the companions on sight because then larian takes away the option to experience all of them.