(sic)

Yes, that's the other side of the issue. It's especially the case with Wingers, where they go narrow in later stages of the attack, instead of providing width. What you are looking for sounds more like a IW rather than an IF. IFs are more focused on off the ball runs and getting into the scoring chances, rather than staying wide and dribbling inside (at least in FM22). If I'm playing with an IF, I'd pretty much always have a WB on that side as well. He's the one that should provide the width at all times, even in the buildup, sitting high and wide - but what happens is that IF is wide and high, and WB is wide and inside of our own half, so I end up having 2 players occupying the flank, at least until the ball progresses into the middle third, and that's something I don't want. I do get them to perform how I want in other areas of play (somewhat, can't expect it to be 100% like in Real-life), just not in the buildup phase. They do occupy the half-space in middle and final thirds. I guess having a WB who's pushing forward on that side and having focus play through the middle helps somewhat with that.

Essentially what you want is a wide player that occupies the channel in possession. I feel for you, as it is something I wanted to have as well, for years. The closest thing is the Raumdeuter. The only problem is, when do they occupy that space? In the final third they will pretty much always do that, even regular Wingers will come narrower and occupy that space often. The issue comes from the earlier buildup phase, where IFs are pretty much sitting wide (with attack duty they might sit a bit narrower, but are much further up the field, pretty much in line with a striker). No matter the instructions, you can't tell them to be as narrow in the buildup, as the roles are simply hardcoded to behave like that. They will sit wider, until at least the middle third, and often the final third. You could try playing with any of the playmaker roles (TQ, AP), as they will tend to move more centrally. A lot of roles suffer from this issue of being hardcoded to behave a certain way in certain phases of play. Usually there are no problems, but when they do rise, it's mostly in the buildup (that's my experience at least). For example Wingbacks in Wingback spots. You'd often see them sit at the half-way line (or a bit higher) during buildup from GK. In FM they're sitting much deeper, and the only way I've found to make them sit higher is to use players in ML/MR spots - but then defense becomes an issue).

It's possible to an extent. With some formations it's easy and straightforward (like the above example of 4-1-4-1 transforming into a 2-3-5). With some formations it's really hard to do (and usually looks lopsided or completely all over the place), or straight up impossible to do. Sadly something like this isn't possible if your 6 is in a central position (they will somewhat cover that space probably, but not nearly as good as a CM in that spot would, they wouldn't be positioned in a line with the other CM). I really wish they'd allow us to at least move central players to the left or right in possession, if they don't want to add separate attacking and defensive formations.