So I killed the thread a few years back, but I'm reviving it again now, as progress is happening and opinions are sought.
Where I'm at with this, concept-wise...
The Big Issues Artistic laziness or inattention to detail back in the early '80s resulted in an appearance that was only vestigially similar from panel to panel, issue to issue; and elements with specific canon reference (characters, props, vessels, etc.) often only somewhat resembling the source.
semi-related to the above, early '80s comic coloring technology and comic colorists/practices resulted in everything with canon reference (i.e., Boba Fett's armor) being grotesquely inaccurate, and usually inconsistent from panel to panel, and issue to issue.
The nature of the costume debuted in issue #68.
Specifics (and my approaches/solutions to them) As I showed earlier in this thread, both the cover and interior artist managed to interpret the partially-visible mythosaur badge on Boba's left shoulder plate in the publicity photo they were working from as a circular badge with a 'T' shape in it. I can see, from the portion of the actual badge that's visible in the photo, how they could have done this, but it's still lazy and wrong. No nice way to soften that.

For armor purposes, I am just going with the good old ESB badge. For this suit, I am going with a pair of beautiful mythosaur sigil patches I found (the symbol shows up on one shoulder, the other, both, and neither throughout Fenn's appearances, and I'm going to put at least one on the left shoulder, maybe both on both shoulders -- we'll see).
Colors... The preponderance of his depictions show him in a hunter green suit with lighter green piping. This is what I'm doing, neck to cuffs. For the armored-up look in the flashback splash panel, I'm going straight ESB Boba as my starting point, fabrics and colors, with the differences that are specifically Fenn -- ammo belt pouches, helmet deco, level of weathering, gauntlets, etc. Since Marve's ESB adaptation depicted Boba with all green body, as in the MSW #68 splash panel, and that's not accurate to the movie, I have no problem adjusting that back to movie colors, and bringing Fenn's armor along, too. Ditto the helmet, which was depicted in the ESB adaptation with white cheeks, which was wrong, and thus I'm doing Fenn's helmet in Boba colors.
Gauntlet blasters... He basically has mirrored versions of Boba's right gauntlet on right and left arms, with different upper mounts than Boba's. No big bulky flamethrower gauntlet. No connecting hoses. The appearance of the blasters varied a bit from panel to panel. I sketched out each one, derived consistent characteristics, drew up plans at 1:1 for the gestalt blaster template, and have hunted up most of the hardware I need to build them.
The suit itself... As said earlier in this thread, everything in MSW #68 makes me feel this is a pressure-suit a la high-altitude pressure suits pilots and early astronauts wore -- a thin sandwich of thermal-regulating material, protective outer layer, skin-adjacent comfort layer. There are areas that look wrinkly, like regularly-behaving fabric, and areas that look stiffer, as though there's something behind the fabric preventing wrinkling. Those semistiff areas are approximately where the hard outer armor plates are -- around the collar area, down the front (with lines and cutouts following the general shapes of the armor plates), upper arms (with even bulkier pads covering the shoulders), and knees. I am making it following the example of real-world pressure and anti-g suits: polyester suiting in hunter green for the outer layer, a lighter green fabric to cover quarter-inch piping for the trimwork, darker green satin for the quilted belly panel. I have thin foam kneepads that fit perfectly as shoulder bells that I'm going to wrap with the hunter green fabric and attach to the sleeves. I have a tab made for the cape attachment on the left shoulder. And I'm looking at other options to aid in comfort (and, ironically, would add some verisimilitude).
Unanswered and/or Unanswerable Questions I am making Boba-style shin tools, even though we never see that low when he's fully armored up. I'll probably leave those pockets empty, but want to have options, in case.
Similarly, I have a lovely pair of JangoWes' Boba boots that I need to weather and add toe spikes to. Again, we never get real good detail shots of his boots, except when he's wearing his "Mandalore Fenn" armor.
My biggest concern is people who will adamantly refuse to accept that an inaccurate depiction should be corrected. As there's a Holiday Special version of Boba, and versions of all the variations over the films -- and also movie and animated versions of Clonetroopers -- I have no problem with someone even doing a "Marvel Comics style" Boba costume, with yellow belly plate, orange half-sleeves, white cheeks on the helmet, etc. It's not accurate to the film, but is accurate to one of the EU depictions. *shrug* But I can't accept it as accurate to the source material, and since Tobbi and Fenn are drawn to more-or-less match Boba in that splash panel, and since Tobbi's armor later in #69 is consistent with his appearance there... well, I have no problem correcting them back to the same movie-accurate coloration as I would with Boba. So I'm building the pressure suit to be an inner layer under the flight suit. I'm using mythosaur skull badge(s) instead of the Circle-T badge. And I'm using ESB colors (and some detailing, such as with the glove appliquιs' quilting) rather than the colors in the comic, where they conflict with canon. I
am using the comics as the primary reference for details and colors that
don't have a depiction in higher canon to contradict them.
I don't know if my approach would ever be approvable here or with the 501st, as the source material is inconsistent and canon-derived elements conflict with canon, but it's how I'm going forward with it. I would appreciate any feedback, suggestions, or opinions that are not attempting to tell me I'm wrong.

Oh, and I've seen some people say he has blond hair. Sorry, Fenn's a ginger -- red hair and blue eyes. You can see him next to Luke in one panel I scanned for this thread and his hair -- which is the same shade, more or less, throughout his Marvel appearances is distinctly redder than Luke's, who
is a blonde.
Once I've gotten some thoughts on this in this thread here (hopefully, some from app team and/or Mercs council members), I'll start a WIP thread. One thing from those weighing in I'd ask for is which board section I should put it in -- Canon armor (cuz this pressure suit isn't "armor" in the sense it's generally used in the club), Soft Goods, Other Costumes...?
--Jonah