Well, here is what I would try. Of course, I haven’t seen this helment so I am visualizing.
You will need to create a MATTE for the helment in AE. And that matte must track with the helmet movement… as the pilot moves his head.
To assist with the trak you could place tracking markers at the 4 corners of the visor… but you will have to paint them out later sinc eyou are doing a refelction and not a total replacement.
Or you can hand roto every frame and adjust as needed. The more movement the more adjustment.
I would make your matte-paintings large enough to give you room to work… are you shooting 16×9 or 4×3?
Once you have your visor matte built you can use it to insert your reflection plates and adjust transparency. Done.