I want the option to avoid PvP altogether...
Simplistically, this could be done by choosing a class for each game session. If you choose something like trader or explorer, all PvP is disabled, similar to a vital NPC in current games. You can't be killed by other players but you can't damage them either, maybe an exception made when you are caught stealing from other players. All other interactions are available, like trading, info sharing, mission giving ("I know a settlement round here that needs a hand...") and co-operation. It is clear to other players that you are untouchable so they won't waste ammo on you. The class stays for as long as your game session so you can't change it on the fly to ambush someone or hide once you kill someone.
Another concern is difficulty level. I am pretty casual but there are those who want the hardcore survival experience - how do you balance both types of player in the same world? While difficulty mainly affects your own stats, how would it work when you are facing a large enemy and the survivalist takes 100 bullets to kill it while the casual takes 40 due to their respective difficulty settings?
It's pretty scummy of Bethesda to only offer the beta to pre-orders when it could be used for those players, like some of us and a lot of the FO fanbase, that want to see how it all works before throwing money at them.