There is nothing preventing a workplace from negotiating a unionized employment contract with a more limited scope such as you describe. I share your desire for

There is nothing preventing a workplace from negotiating a unionized employment contract with a more limited scope such as you describe. I share your desire for something less rigid than the (very real!) unions which match the stereotype you describe. Though I would like some intermediate restrictions on the ability of an employer to summarily fire an employee for no good reason, short of extreme difficulty. Like, maybe some advance notice or severance payment in the absence of misconduct - the unemployment insurance regime is often severely inadequate, and gaps in employment make it harder to obtain subsequent jobs. Plus some chance to refute allegations of underperformance makes sense - it can be real underperformance or it can be a cover for discrimination, both happen.