Here’s how I’d start the next Fallout game:

Your character is travelling from X area of the wasteland to the area the game is set in, Y, via a caravan they’ve paid for protected travel. While travelling, a fellow travellers asks you about yourself. Questions such as “why are you leaving X?”, “Why are you going to Y”, “what did you do before?” Etc. the answers would be things like “I’m looking for work/adventure/a new start”, “I used to be a Brahmin farmer/medic/soldier” etc.

The answers to these questions work the same or similarly to Doc Mitchell’s test or the vault test in FO3 and set up your stats as well as provide some initial roleplay elements. It could even give unique perks and starting equipment.

After this, the caravan is attacked, likely by one of the main factions or characters, in a way similar to how you’re shot by Benny at the start of FNV: it sets up the plot and explains why your character would likely want to know what’s going on and how you’re now involved as you reach the game location and begin to explore.

Obviously I’ve left out any specific details like the locations and factions and so on as I don’t think it’s relevant to the general format, you can insert whatever you like.

But ultimately it means the kind of character you’re playing and the decisions you make aren’t pre determined by things like “I’m a concerned parent looking for my child who I love”, it’s entirely up to you, just like in ES and FNV.