My character just picked up some randomly- looted Synth armor that came with some Misc mods (Leaded, Eric.), and I was looking at removing them. Unfortunately, there was no 'None' option to do so. Now, my game is modded, so it's possible that this issue is caused by one of them, but I thought I'd ask people who don't have mods just in case: is this an issue with Synth armor in the base game, or is it just a result of one of my mods?

Just use the least costly mod to remove them like with Ballistic weave.