Have you seen it?
I have, thank you.
Take for example the Shiawase Monsoon and Rain. Based on the design of the stock, you would need to hipfire to get any benefit from the sights.
They do have an interesting design, that's for sure. However the Monsoon does come with a Smartlink, which means the ergonomics of the firearm can change without as much of an impact on its intended user. The Rain also has an extended stock, it appears that the shotgun is in its retracted state. I'm curious to see what the extended state is. If it's straight back, then I would agree with you. If it pops back and up, I might be inclined to lean towards the shotgun being fine for its intended audience: ignorant homeowners.
The Cavalier Falchion looks like something a toddler would draw if asked to draw a picture of a rifle.
The Falchion is a rather basic looking weapon, one that matches up with the standard upgrades listed for it. I for one would not want to see a lot of doo-dads hanging off of a rifle intended to be used as a club if need be, that's just something else to break off.
I don't think it's physically possible to fire the Rainforest Carbine unless you are a Dwarf based on the 3" stock and extremely small foregrip area.
I don't see anything in the book listing the size of the Rain Forest Carbine, I'm not sure where you're coming up with that stock length. Please note this is another firearm that features a retractable stock, we don't know if the stock is in the extended or retracted state. That being said, I do have a slight issue with the artwork: I would bring the trigger down slightly, so that it is below the lower rail of the stock rather than halfway through. However that's a minor quibble.
A question for you: when you looked at the artwork did you also look at their upgrades? Or did you simply look at the art? From your listed examples I would think that you simply looked at the art independant of the game stats.
You're ok with paying real life money for a PDF of inferior products, I'm not. There are plenty of bad guns in the SR5 core book to choose from.
Power creep is dangerously easy in crunch books. Something that Jason needs to have a good handle on not only with the core books coming out but for future books down the line. If a book like Gun H(e)aven 3 simply one-ups the core book then SR5 runs the risk of turning into Rifts. If I want to play Rifts, I'll play Rifts. I like that SR5 balances the weapons out in order to give me a good variety of a few basic concepts rather than just giving me a few optimal choices and a bunch of GM weapons.