Galling usually only happens when you have stainless steel nuts and bolts of similar hardness. For example if you use a 316 bolt with a 17-4PH nut you shouldn't have galling. You can also use a thread lubricant to prevent galling.

Another option is thermal set inserts such as Dodge Ultrasert http://www.stanleyengineeredfastening.com/brands/dodge/threaded-inserts/ultrasert

I have used these extensively in plastic, mostly in 3D printed parts. You can install them with a soldering iron quite easily and I find them to be better than Helicoils in plastic.