So in short, the Crusader Era is broken into Early (EC) and Late (LC). Early Crusaders are bone and leather "caveman" kits, Late is KOTOR comics and game. It used to just mean "before the Boba timeframe" which is why they got lumped together, but now that we have multiple Moderns and a Post-Imperial and Legacy, they could and perhaps should some day be split out, but that's irrelevant right now. For now, for your purposes, consider "Crusader" to mean anything before Boba Fett and "Late Crusader" to mean "after bone and leather were obsolete".
The main thing about the LC kits is that they were said to be custom handmade pieces by/for each mando, not a uniform, so every Crusader's plates will be unique. That makes it very hard to give style advice and leaves it up to the recruit to communicate their ideas and get approval before committing too far. The best advice we can give is to get some sketches going, ask specific questions, and look at the existing kits (reference images and approved kits) to get a feel for the aesthetic. If you are building a Modern kit, you can get a hard yes or no because the plates are pretty much all the same.
You already know that helmet will work and the plates are along the right lines so I'll drop some tips.
Some common LC style elements:
- Hoses: Crusaders loved hoses on their helmets. (I believe in-universe it was before sealed space suits so they used life support systems, but may be mistaken)
- Large plates.: You almost always see single-piece chest plates and large ab plates in this era. Your sample chest plate is a great example.
- Melee weapons: Not mandatory, but you will notice a lot of them in canon references carried a melee weapon of some sort either in addition to a blaster or instead of a blaster. For my kit, the hardest part was actually the blaster. My blaster design got sent back for a few reworks because it "didn't feel era-appropriate" but that wasn't/isn't really defined anywhere. I say that mainly to say this: do not expect to use any recognizable modern blaster. A staff of sword may well be your easiest bet for an approvable weapon.
- Furs and spikes: Don't go full caveman on the furs, but a cape or kama from fur would likely not be a terrible idea for an LC. Shoulder spikes are worth considering as well. See Rohlan Dyre for a few examples of how those might look. Depending on who drew the particular panel, his shoulder spikes looked all sorts of different ways

- Leather: avoid nylon belts and other synthetic materials. Again, don't go full caveman, but leather belts and straps go a long way in this era to make it look less modern
A final note for now, be careful how closely you emulate an approved member's LC kit. As I said above, every LC's armor was custom made for the warrior and members put a lot of research, time, and effort into making a truly unique design that will fit within the aesthetic. I'd recommend you try to base it off of comic or game references more than off of an approved kit.