You could put the accessories (optic, bipod, sling) on their own texture sheets if they're genuinely modular pieces that could be re-used on other weapons.
If this is for a first person weapon then you should do the scratches in zbrush or mudbox. It's pretty quick and easy to do this and will be a noticeable improvement in quality for something close to camera.
Quick update. Been really busy lately but still determined to finish this project. Made the pommel gem a raw sapphire and beat up the weapon in zbrush.
Thanks! Didnt know the company "Fowler Industries" until you told me. Looks like there is a big competition going on when it comes to weapon customization.
I decided to make a weapon instead for Elder titan so here are the final results. link to submission http://steamcommunity.com/sharedfiles/filedetails/?id=245676021