As it was said in the beginning of the topic, i think the better deal is to have fallout 1 & 2 (mixed or not) with some features from Fonline, like real time, slavery, vehicles, crafting, companions etc...
Because all that territory, that engine, without big quest and storyline, you will lack of goals.
Fonline is somehow, made for players to interract, meet, trade, compete, fight, or help each others.
Without other players, known and unknown, a lot of feature would lose any sense.
I personnally don't like the percentage of pk (and trollers especially) but i think they're needed too, to fit with the wasteland, and add more value to everything you can save from them.
Problem is there not much feature to make the game easier and interresting for newcomer.
Something should be made to encourage them to stay more than a month.