For the Aimed Shot option I remember someone suggesting that in addition to +1 to hit it also added +1 to weapon power. I liked that idea, but have not play tested it.
An option I have used for long barreled weapons in my Car Wars games is that aiming gives a bonus to hit and also extends the range of the weapon by a few inches.
For Wastelands I would recommend extending the range of all weapons by 3” to 4” for an Aimed Shot. This keeps the Sniper Rifle from having too great a range extension, but adds a nice range increment to shorter ranged weapons that could give the wielder a good, but not overwhelming, advantage.