I think so. The triadic system is almost designed to make the Bronze MAge's player angry. "Pick three spells. OK, now you can NEVER have two of them. Why? Because TRIAD!"
I think that would be better.I am not sure what you mean by "hard rules" - rules where the DM does not apply his discretion? If so, then maybe the surviving spell of a triad could be chosen at random. Then you wouldn't have any DM discretion or incitements to Player vs DM conflict.
I think it's easier to nerf the sorcerer wholesale. "No spells above level 5. Here's what you CAN do with those spell slots: ........."Long story short, I think the bronze mage is less unbalancing than a sorcerer. Maybe that's damning with faint praise?