Vanilla trader window has HUGE limits. It only shows a few of weapons and works in a weird chance-wave system that is incredibly flawed. Current trader offer is made to allow you to have "everyday" access to basic weapons, and only ocassional access to high-end weaponry. However due to "wave" system the calculated chances for some weapons to appear are skewed. This might mean that you will never see your favourite weapon in traders' offer thorought your whole playthrough.
While some weapons are locked out in the beggining, by the half of the game (around the moment where you finish inspecting last helicopter) you should be able to access every weapon without skewing balance. In this case, I wouldn't call spawning weapon or increasing chance of it appearing in traders' offer as cheating, but as a workaround that might sometimes be needed in order to have an enjoyable experience.
To increase chances of weapons' appearing in traders' offer:
1. Go to gamedata/configs/misc/trade
2. Find file of trader you want to edit, open it with notepad++
3. cltr+f [supplies_generic]
4. Scroll down and find a weapon you want to edit. Second number is chance. Set it for 0.5 for 50% chance, to 1.0 for 100% chance.
Or: spawn yourself a weapon
1. Go to gamedata/configs/debug
2. Open xrs_debug_tools.ltx with notepad++
3. Change line from enable = false to enable = true
4. Load your save, press esc to go to main menu, press S. Type code name of your weapon into spawn box, for example wpn_ak74
Sometimes weapons' actual name is different, for example code for standard AK-74 with solid stock is wpn_ak74s while for AKS-74 with folding stock it's wpn_ak74. Sometimes names are completely off, and you'll have to find that weapon on a list to know how it is actually named. To find a list of weapon names open any trader file and scroll down, there is a list of all weapons in game. This controls the prices and every weapon must be added there, therefore it can be used as a "cheat sheet" for spawning.
