So...in plain English are you asking about non-combat abilities for fighters?
In the OP, it is stated more generally - more space for everyone who isn't a spellcaster - the idea being that spellcasters dominate narrative space, in general.
Here's an example: I play in a Star Wars Saga Edition game. All five PCs are Force-users. When we started making characters, three wanted to be "fighty", one wanted to be our social-primary, and that left the rest (piloting, mechanics, knowledge skills) to me. When all was said and done, when combat started... I didn't have a lot to do. I had a bundle of hit points, so I was in no danger of dying, but having not optimized for combat, compared to the three who were optimized, my contribution just wasn't relevant.
So, that may be a way to put it - "narrative space" may vaguely correspond to "relevance". He's asking, in general, for ways for non-spellcasters to be *relevant* to play more of the time, across many types of situations, rather than relevant just within their specialization.
Now, I'm of two minds on that. One is that yes, you don't want players to be bored, and players who feel they are not relevant stop trying and get bored. On the other hand, if you build a character that is specialized, you should
expect that they'll be really good in their specialization, but not so hot outside that specialization. Don't cry when you get what you ask for!
The D&D fighter does to some seem to have the particular problem (depending upon edition) that they don't really dole out the most damage in a fight, nor do they have skills useful outside combat. So, they are specialized, but not so impressive within that specialty either. That can be a problem.
Now, we could ask for mechanical cures for this. However, we should note that there are solutions that lie elsewhere. For example, sometimes you can handle such issues in adventure design. For my Star Wars character, the problem is solved when there are goals in combat that aren't about the actual fight. I can pursue those, while the fighty characters are busy with all the fighting.