No doubt this topic's been thrown around the dev team a lot and I understand the limitations that have been brought up in other topics, but I felt that what I'm about to suggest -may- be applicable to the current weapon roster regardless, though it would really benefit by a considerably larger weapon list in the future. The idea I have is to make gun manufacturing as an Engineer a little more difficult. 'Cus at present it just seems a little too simple to me. Gain the supplies and you can make a weapon, just like that. I propose something similar to what the Cultivator currently has going, where the player needs specific tools in order to make specific food. This could work quite well with the Engineer, making it a requirement that said Engineer must invest in specific tools in order to create specific weapons.
Not only do I feel this will make the class feel more specialised, rather than something you just quickly switch to in order to arm up, I also think it will help prevent new players and potential griefers/minges from getting the good stuff too early. A savvy or determined scavenger can easily gather up all the resources needed to make things like an SMG LOST or a shotgun with some ammo in about an hour or so worth of gameplay. Those people who've only been here an hour should really only be trusted with a handgun or at the very most a Scrap MP in my opinion. That way if a Minge does join they're not going to be very well armed.
Another thought I had regarding the current weapon manufacturing system is to make it so that more weapons can be unlocked as you increase in the Engineers class specific skill. This will help limit transactions of the high power weapons greatly I feel. Only the truly devoted and trustworthy players would make it to the final tier of this skill and in doing so getting access to the best weapons around. And you'd be comfortable with letting them, as getting to that stage would've taken a LONG time so by then they will have either became trusted and well respected members of the community, or outed as total mingebags and banned from the server before they can get there.
So... Thoughts?

