posting here to comment later! I may have some insight with being Q+A Director and App Team
Welcome to my madness!

Looking forward to hearing from you.
As for the elastic, while the section of the CRLs I quoted was indeed for armor, it is also states the ONLY places that elastic is allowed to be shown on a kit. I appreciate that you have gotten your kit approved this way, the CRLs are ever changing and these rules may not have been in place in 2010. Kits built today will need to follow the current CRLs. When those get updated, then those will be the new CRLs. There is no grandfathering unless otherwise noted.
Noted

I was still in the build process when the most recent update was applied to the CRLs so I have already gone through changing elements to meet the updated CRLs.
Elastic is not listed as an acceptable closure type.
True. It's also not listed as being unapprovable. So question here, my OM vest has chain mail as the side closures (part of my brigades upgrades) which is not a listed approvable closure method but has been approved by the Brigades app team and my Ruus' before we lost him, does that take it out of compliance? Because that is probably my second favorite aspect of my active kit and I would rather retire it before replacing it.
My suggestion was to have a leather strap with elastic attached to each end. The leather would be the only visible part, and the elastic would be under your vest material. This would still give you some stretch, while only showing the leather portion.
I definitely didn't understand your suggestion the first time. I think I've got it now. My thought was something more like this (that's just a leather scrap I put on top to give the idea).

My thought was that it covers the majority of the elastic but should still give me enough stretch to avoid an attack. I do not handle restrictive pressure on my ribs well. And if anyone other then a Ruus' or app team member notices the tiny bit of elastic showing, they are staring too long somewhere they shouldn't be. I also don't walk around with my arms up so it would be concealed most of the time in general. What do you think?
I'm totally down to keep brainstorming this, and if I end up with grey scrunchies so be it.
Since the elastic is sewn in-between the fabric layers and the quilting was done on top of it, it would be faster to just remake the vest then to try and move it.
I am a member of the Education team and have been training Ruus'alore and Ruus'alor Sol'yce for about 3 years now. I mention this in regard to your elastic because it is one of the things they are trained to be on the look out for.
My suggestion to you would be to reach out to both your Regional Ruus'sol and use the App Team Q&A to have them weigh in on the answer. This way you can give you recruits the best information.
Wouldn't happen to be interested in training another would ya?
I have actually already reached out the Ruus'alor and Ruus'alror Sol'yce in the surrounding clans (I've got three so far that are cool with me shooting them questions) so I am currently building a network of information. I have also run into an apps team member who gave me the go ahead to bounce stuff that way. (While trooping, in my kit). Usually I can find the answers I need in the Q & A section without having to actually ask the question and add to the apps teams workload, or one of the other Ruus' know the answer. I just didn't realize this was a question I needed to ask. I had seen it on approved kits and it met my physical and psychological needs. It wasn't directly address in the CRLs in relationship to vests, so why would I question what appeared to be an already established acceptable method?
The most frustrating part of this is that I spent a year building and then the last year trooping and I never knew this. Please tell me there is hand book or pamphlet or something for the Ruus'alor Sol'yce position, because I do not want to be the reason someone doesn't get approved.
And while we're still on the topic of elastic. I was planning on building in some elastic relief panels into my spats/half chaps to improve the fit and help them stay in place. It would look something like this.

I had planned to put them in the back/slightly toward the inside of the calf so they wouldn't be easily seen but in the area where the stretch would be the most beneficial. Aka, where all my equestrian half chaps have elastic. But it does leave little slivers of elastic visible. Its probably 1/5" maybe less. I'm guessing here. Is that also going to be a problem? It greatly improves the fit and comfort for half chaps to have them there, but I can design without them, it just won't look quite as nicely fitted. I was also thinking of running a zipper up the back seam but if I can't put the elastic in that will have to change because that is a fight I am not interested in every time I kit up.