Our MPP coilovers were always designed with the intent that the user also wanted to lower their Model Y. Somewhere along the way, a large percentage of our sales started coming because customers realized our suspension kit actually rides better than the OEM suspension, despite the lowered ride height!
We're a performance-focused company first and foremost, and while I agree the Model Y ride quality isn't up to the standard it should be, the dampers and springs are only a part of the system that make up the ride quality you experience.
Proof of that is that we had to work MUCH harder on our Model Y suspension kit to get the ride quality close to the Model 3. There are many factors, but no doubt the Model Y ride is significantly more jarring from the factory than the 3.
What I'm saying is that we are open to slightly softer springs, if the ride height can be higher so that the vehicle has acceptable travel before engaging the bump stops. But, when we start straying too far away from a "sporty" yet refined driving vehicle we're starting to get outside of our expertise and our passion. We don't particularly want to make cars that ride like a 90's Lexus (although they are SUPER comfortable and silent, impressively so!)
My honest feeling is that the somewhat harsh OEM ride quality is significantly affected by other components than just the dampers and the springs. The reason I feel this way is that the ride quality on smooth bumps is actually very good, even on very large bumps. If there are smooth ramps into and out of the bump - the ride is impressively supple. The problem is when there are sharp edges on the bumps, such as potholes and cracks in the road.
These kinds of impacts are absorbed not just by the dampers, but by the geometry of the suspension and the stiffness of the suspension link bushings (and of course, the tires). Without having done a complete study it's hard to say with any certainty, but my feeling is that this geometry is causing a lot of the harshness as a larger proportion of the impact is going into the relatively stiff bushings, rather than being directed into the damper.
Add to that the low mass of Tesla vehicles in general, the glass roof, and the open rear cabin (where the rear suspension is not isolated by a rear deck lid), and you have a lot of noise, which as mentioned above, translates into a perceived rougher ride. My experience is that if you drive your Y with loud music, it feels like the ride is smoother. This is because our brains interpret sound as roughness (which is likely why NVH is all categorized together - noise, vibration, harshness).
This post is more about education about the platform than it is a real answer to your question, so I apologize for that. But yes, we can look at a "soft spring kit" as a separate product option, but my feeling is that you'll lose more in the feeling of the car than you'll gain in ride quality, due to the points above!