Huh I also have a "developer" mind, and very few people would call me a designer, and those that do should re-think what a designer is.
However, from my observations over the years, the cost of "browser specific" behaviors is equal to or less than the cost of learning entirely new styling paradigms every time someone puts out a new UI framework. CSS also has the benefit that over time browser specific behaviors fade away as standards take shape, which is inherently not the case with UI frameworks.
As far as the namespace goes - I guess, but there is nothing to stop you from coming up with your own namespacing scheme using nested CSS classes.
However, from my observations over the years, the cost of "browser specific" behaviors is equal to or less than the cost of learning entirely new styling paradigms every time someone puts out a new UI framework. CSS also has the benefit that over time browser specific behaviors fade away as standards take shape, which is inherently not the case with UI frameworks.
As far as the namespace goes - I guess, but there is nothing to stop you from coming up with your own namespacing scheme using nested CSS classes.