Well I don't have a large sample of es1a. I can only speak for myself. The first one arrived with a tilted right driver and a headband with failing paints. The seller was nice and responsive though. He swapped me with a new set. drivers were fine this time, but the headband was still with failing paints. Sent me a sperate headband. Used for a month or so. Didn't fail this time but I doubt how long it's going to last. The paint of the headband doesn't look sturdy at all. I might be biased because of the back and forth. The earpads also mounted in a stupid way. Base plate under the earpads tilted up if you don't use a glue to fix it. In general, build quality of both side earcups are fine to me, but not the headband. It just feels like a cheap DIY unit instead of a well built product.
The point I want to make here is that it might be a better idea to get a 009 or 007 if you only plan to get one single electrostatic earspeaker. The es1a sounds just fine to me, but the build quality is not up to that level.
I do think the original Omega design limited them(or him) to design something better built. I personally can't think of a reason why it has to look like an Omega though. If you are making some crap like Hifiman R10 then there might be a reason to steal the fame of sony and bump up the sale. If you can design something sound decent enough just like this one, shouldn't it be a much better idea to just start with a new design instead of borrowing something a few decades old?