The trouble with "more weapons" is that the game starts to become an action game instead of survival horror.
I wouldn't agree on that. I'd say that how your character can interact within the environment is more likely to affect how much of an action game it becomes. You can give a person many weapons, doesn't mean they are a fighting fit soldier from them. If they start doing silly things like putting in a jump button or suddenly you have proficient combat handling then it would wreck the effect.
Things like a katana or a taser are so uncommon and scarce that it seems unrealistic for your character to find them and it takes away the difficulty (and therefore the fear factor) of the game.
I don't agree on this either. First off, it assumes these weapons are more powerful than other melee types. A katana would probably be less effective against multiple opponents than the bludgeoning power of a bat. A taser fires a charge which you'd need to reload. Very useful when you want to take down a semi powerful opponent, but the ammo would be rarer than Magnum Rounds in a old RE titles (since you were so nice to pronounce the scarcity of tasers).
The point of these is to give players options, and potentially something to strive for. They aren't melee replacements, or rather, they aren't necessarily good replacements. Just variety.
The same goes for normal weapons- there shouldn't be a huge amount of different and high tech guns as it takes away the challenge and realism of the game.
Didn't stop a high caliber turret mini-game existing out the front of Buckingham.
Stronger firearms could exist in the game. It depends on how the developers make it so that they did exist in the game. I'm sure the rest of the world will just sit idly by while London turns into a decaying cesspit.
They should attempt to bring in a psychological effect. (Perhaps not when fighting zombies because that's kind of a given. You shoot the ****ers, they're gonna kill you if you don't). I'm referring to when you interact with other NPC's. Not everyone is going to have their head screwed on tight during a zombie apocalypse. You can choose to eat all the words they feed you, or ignore them. At the end of the day you're a survivor amongst others and you want to be the one who lives through the nightmare. Your decisions can affect who lives and who dies, with a chance of a perfect playthrough available.