Interesting idea. What sort of level of magic are we talking about? Level 3 fighters with +5 swords? That wouldn't necessarily be OP imo.
You're right that non-casters are much more gear dependent. That's probably true in every edition of the game, purely because in D&D magic weapons and armor have always allowed the fighter to do what he does much more effectively.
At levels 1-4 though aren't fighters and barbarians more powerful than casters anyway? I guess it depends on how many encounters there are per day. In our recent D&D games we haven't used dungeons much so often there was only one encounter per day, which meant even low level casters were still very effective.