... What have I (bleep)ing done! I've sparked inspiration! XD Okay, so I would have to explain a couple of things about making your own helmet that I had to learn and am STILL learning because I am personally chasing after perfection!
First, thing first is that you are going to need a male human head. I had to generate one using the MakeHuman program in order to get the sizing of the helmet properly measured. That means that you will have to size it up to where the model can see out of it. If the digital dummy can't see it out of it, then you won't see it either.
Second, start thinking about how you are going to put it on and taking it off. That means that you are going to create a seam line somewhere on the helmet. I'm thinking about the area of the helmet where it has its second elevation. That is just a suggestion. If you can, get references of that ranger helmet. As many as you can. Once you get an universal consensus on where to open up the helmet, follow it in Blender and see how it goes.
Third, make sure that you have universal thickness on the helmet. If you are planning on using the helmet straight from the printer with out creating any molds, like I'm trying to figure out how to do, then make sure that it is at least three or four millimeters minimum. That means you are going to have to create an inner shell in order to give the helmet more strength.
Finally, the last thing you are going to need to do is to create more detail. When you rip a game model from a game, it's going to have a lot of low polygons, but this is a model to model basis. Some will give you more polygons while others give you less. This is where topology of the model is important because if it has too many triangles at different parts, you are not going to get a smoother print and that means more sanding and prep time before you can start painting...
ONE MORE TING!
Save duplicate copies of your file! If you get to a point to where you want to try something new, save a new file from where you worked so far and try it out. If the idea goes straight to hell, you can delete it and go back as if it never happened. For example, you saved your file with the name, " Yellow Hyperforce Ranger 11_23_2020" and you want to try something new, you can deviate from it try it out. If it works, continue from that point forward.
That's that I did and it prevented me from starting back at a different point of the modeling process.
That's a couple of hints I can give to you right now. I'm in the process of making some patterns for my suit so it's going to be some time before it's almost done. I might make a tutorial from start to finish depending on how it turns out since there isn't an actual tutorial on Youtube to do one. I'll just have to wait and see. For now, good luck and if you have any more questions, you can invoke my name again and I'll try my best to answer them.