I'll just say this and no more:

If this is about Garrett we know, then make it about Garrett we know. Respect his established story, his world, his arc, his chronology, his acquaintances, and so on. If not, change the character's name or set the story up front as an alternate universe kind of thing, or else it will just clash with everyone's personal notions. It makes no sense to go with a prequel of THE Mr. Garrett, and empower him beyond what he has available to him in the days before the Bafford job. At least those of us who will know even this much of this fan project's intentions, if it's ever completed and shared, will know right off that it deviates in many key points from the first second, and will likely further deviate and diverge from much we find familiar and familial, and will have been warned for better or worse. I will not be shocked or affronted, therefore.

While I expect it to be inventive and have clever moments, it will no doubt never make sense to me, personally, why Garrett, and The City, and this period of time in HIS life were the focus of a new story, if this story's take on the character's development and the tech available to him at any given point aren't beholden to much of what we know of them. He's bad ass, and not because of tech or devices. He was impressive without Keeper training, and without tech, but needed more to become successful, and have self-imposed rent issues, rather than seriously barely eating enough.

I will never understand, until it's finally explained, why the restrictions imposed by The City and its tech, the idiom of the factions, the character of Garrett, no matter how powerful and skilled Garrett is all by himself, with no devices, with only light and shadow and trickery and ego, are considered by many creative persons to be stifling, not a delicious challenge with so many complex avenues to explore that don't ignore anything, yet stay true to what Garrett would know at that point, mindful of what he could not know. There's so much to mine and so much to expand without adding in new devices or character traits. It could be great and inventive and keeping to the established elements.

With projects like these, I always wonder who the intended audience is and why it's brought up before fans, not those who would eat it up and not question it from a seasoned perspective. If the established concepts are boring or stifling, start fresh, or call it what it is: an alternative game for those who never really got into what the devs were doing, or a reboot.

I know I'm in a tiny minority, but just make an FM or campaign, and you'll have players, regardless of what you invent, impose, twist, or personalize for your own satisfaction. The fiction won't be taken too seriously, unless it's surprising in a delightful way, so it's best if you marry the level design well to whatever is written, and don't write too much for readables, as it's generally considered not fun to read and read, nevermind the translation issues. Just getting it done is a huge accomplishment that deserves its own respect.

The potential is already in place without yanking it into a confrontational, combative, action-oriented game, where stealth is only an option, instead of the other way around.