Is the usage of "one" instead of an article in a sentence meant for stressing on the importance of the following noun?
There is the 'one of several [in a subset]' sense, where 'a' doesn't carry this connotation so strongly:
- Although many new models are not gaining popularity, there are several that buck the trend. Consider the Zeta Supervac. It is one model which is gaining reputation recently.
But there is also another usage – as you hint, an emphasising usage – one of a kind even [in the universal set] where 'a' would sound weak:
- Although hardly any new models are gaining popularity, consider the Zeta Supervac. It is one model which is gaining reputation recently.