Then you bought the wrong game. There's no point in this game if you aren't the Dragonborn. I saw a mod like this and just thought why the hell would someone want to do that?

Nyankhajit, are you talking about the clue where you can find the first butcher's journal inside the butcher's shop in that chest? Yeah I tried doing that on my second play through to see if I could just skip to the part where he gets arrested or killed, but nope, game wants me to accuse wuunferth still and either lock him up or go right to the gray quarter at night.

You don't have to do that. You can confront Wuunferth directly (even though the questline doesn't give you this option) and tell him about the journals and the amulet. He will tell you who's really behind the murders and you avoid the whole part where you send him to jail for no reason (even though he never gets upset about it; he'll continue to train you while he's in jail, lol).

Yeah I know you can bypass sending him to jail but you still have the point that you can't outright arrest/kill the butcher after finding his journal in a semi-hidden chest inside his own shop, along with the murder weapons he used. You still have to patrol the gray quarter and catch him in the act.

''Be what you want, do what you want''

As long as you want slay dragons and be labelled 'Dragonborn'

I suspect this is less to do with story and more to do with technical limitations. Namely, the voicelines and other support for the western watchtower and subsequent meeting were probably only recorded for Balgruuf and his retainers, or perhaps they just didn't have time to finish scripting the event using Vignar and his associates as an alternative, so they have to get that event out of the way before there's a possibility of Balgruuf being replaced.

Maybe someone with the toolset can check to see whether appropriate lines of dialogue for Vignar are buried in the data files?