WWCAJD - Vapor Barrier Replacement

So I am getting a little OCD here and want to replace the two vapor barriers in each door

Small Vapor Barrier: this one is easy, simple rectangle out of 3/16" ABS with radiused corners held in place with rivnuts, sealed with butyl, CLD on outside, and CCF on interior side

The large hole is a bit more work:
Attachment 14344 Attachment 14342 Attachment 14343 Attachment 14345 Attachment 14346

When I decided to do this, I had not realized just how 3D this was, I knew it wasn't flat but I was thinking the same ABS above and then I would just heat it and bend it to my will whereever I needed more room. However, once I started looking at it, I knew that wasn't going to work. Between the deeper part of the back of the door panel and the curves on the door's inner skin at the opening its more then just bending some heated ABS in place

The right thing would be to fiberglass it over the door panel and vapor barrier itself but that is something I have never done.
For those that fiberglassed your large door openings, how thick do you need to get for it to be effective?

So next thought is to piece to it together from Expanded PVC or ABS

The expanded PVC would be easier to work with but the 1/4 IN is likely not stiff enough the the 1/2 IN gets tight to make some of the dimensions

Once I get something I want to do in my head its tough for me to bail on it but I am wondering if the benefit of sealing the doors is worth the effort this will be. I already have the rivnut driver on the way and have the rest of the hardware needed so at a minimum I will replace the small one, even if the benefit is reduced if I don't do the large opening.

To ease fabrication, I could build a "box" that's 2" deep all the way around and then where its shallower cut out that area the of the box and then cover/seal off those penetrations that are about 1" inside the panel

Would love to hear any other ideas or stories about your results of sealing your doors to this extent (Note: CLD in process and also installing inner sheetmetal CLD from the door cavity side, not the interior side, as much as possible)

Edit: just writing this out is helping already, another option could be to use the ABS for the main back piece and the trim around the opening and then use Expanded PVC for the 2" portion to give the box its depth?