Since that tie is also maintained by large amounts of political donations, it's going to be a hard one to break.
Sure it cuts down on individual choice, but it should theoretically be the most cost efficient method, both for the employees and the insurance company.
Selection of plans or providers is not the problem, especially with the current popularity of PPO plans.
Even the marketing act of splitting up all these groups up as you describe is a huge waste. Now you have to shop the differences, the companies have to explain the differences, and everyone (insurance co, health provider, patients) gets to track multiple different groups with different rules. It's all a waste compared to fewer larger distributed risk pools - which is the whole point of insurance.
The only for most Americans to have a choice in their health insurance is when they get to pick between the plans from either husband's or the wife's employers.
The biggest disappointment of the Republican alternative to Obamacare was not coming up with a way to sever that tie.