I've generated a map with seed 340 and there aren't a lot of positives.
The nearest oil is barely visible near the top right.
With all the cliffs the starting area has little space for my magnificent main bus.
The nearest stone to replace the tiny 81k starter vein is sure to attract some unwanted ...

it will be very annoying to have to do this, because if i need ammo or new fuel for my tank or whatever, i will need to go back to old world, somehow delete ammo, go to new world, and then cheat in ammo. And even worse: Using turrets (i heard it was a very good strategy to place alot of turrets ...

I didn't even think about creating the enemies myself, but is there a way to create enemies all over the map in a way that the factorio map generator would do it? because if i just go around creating my own bases that kinda defeats the purpose of exploring the map for said enemy bases and because ...

Don't think it's possible to change map generator settings for a running game. If it feels less cheaty to you, maybe create some enemy spawners with something like
for x = 1, 4 do
for y = 1, 4 do
game.player.surface.create_entity{name="biter-spawner", position={game.player.position.x-50+x*6 ...

You could try using Peace Mod - https://forums.factorio.com/forum/viewtopic.php?f=87&t=8344&start=40#p92300 . It creates patches of ore that can be mined and turned into artifacts. You would ave to create patch of it with console command though so I'm not sure if you wont consider this cheating.
I ...

So, When is started a game i turned off enemy bases because i didn't want to worry about enemies attacking me when i was building the most amazing factory of all factories, not knowing that you would need aliën artifacts to create purple science packs. But i still want to complete the game (create ...