[survival mode?]

Sounds like an awesome idea, you got my vote

[Zombie Variants]

I love the idea of a howler, also maybe making them look like normal zombies, so your always paranoid when fighting

[Scope Suggestion]

Good idea, I'm just not sure how exactly pz developers would implement it

Maybe a fisheye effect?

[Crafting and Building suggestions]

I guess that improvised cannons/ ranged weapons would be a little OP, but it would take many reasorces and lots of time and skill to craft then, and even then they have limited use.

[Crafting and Building suggestions]

I think improvised weapons have almost been completely ignored in this game so far, excluding random objects and the famous spiked bat; I think components should be item drops (pipes, wires, electronics, poles, rebar, etc.), which can be crafted into creative and brain bashingly fun alternatives to the standard baseball bat and frying pan. Components and junk parts can be found in crates, trash, and in items that can be dismantled (adding more usefulness to items like the screwdriver), and can be interchanged when constructing. Maybe this can be expanded into a skill, with the higher levels allowing you to build more complex and dangerous weapons of mass de-zombification (broomstick with knife taped to end is easier to make than a lethal taser/ hand cannon).

Item ideas-

broomstick, wires, electronic scraps, gears, screws, bolts, pipes, tapes, springs, etc.

Weapon ideas-

broomstick+fork+ripped sheets= crappy spear

Propane tank+pipe+tubing+electronic scraps= flamethrower, or a gas powered nail gun

Pipe+wiring+battery++electronic scraps+nails= lethal taser

Also, I think wiring and piping should be incorporated into base making for better infrastructure

An example would be water collection barrels with pipes leading indoors into storage barrel/dispenser

[High Risk combat]

Maybe this is against what project zomboid is about but aren't the zombies a bit too strong? I mean, some can take 10-20 hits with a crowbar without event falling down- I think zombies should succumb with 1-5 well place blows, but have a higher chance to injure you if you mess up.

Also, when sneaking up behind a zombie, one strike to the head should be fatal (well, fatal enough to kill them again).