I think that properly answer this question you need to start with an agreement defining what we are actually discussing. When I look at the collection of criteria, “modern day”, “bluewater sailboat” and “25-30 foot range” these collection of attributes seem almost mutually exclusive from my point of view. It is not that you can’t design a 25-30 foot bluewater cruiser, but pretty much by definition it would not be modern. (Yes, I know that was a double-negative but this is after-all the internet)
In my mind, by definition the term blue-water implies a boat that is optimized for distance voyaging. That boat would be different in my mind than a boat that was merely capable of making distant open water passages. Many boats can make a transoceanic passage with a bit of luck and a skilled crew. But to be optimized for distance voyaging, the boat would need a certain amount of self-reliance, robustness and capacity to carry all of the gear and consumables that the crew would need to make a long distance voyage.
As a rule of thumb that means the boat needs something like 4,500 lbs to 11,000 lbs (2000 kg. to 4989 kg.) of displacement per person. In the past, boats derived from traditional working water craft may have been able to carry that kind of displacement in 25-30 length on deck. But by definition, modern designs aim at L/D’s somewhere in the 110 to 165 range, with 165 actually being considered pretty heavy. That would suggest that at the light end a 4,500 lb, modern single-handed distance cruiser would have a 23 to 26 foot waterline, but at the high end, an 11,000 lb modern single hander would have a waterline in the 31 to 35 feet in length. If this were a double hander minimally it would have a waterline length around 29 feet, more optimally somewhere 37 feet, and at the high end of the load range, a truly ‘modern day’ cruiser for a couple would displace something less than 22,000 and have as much as 45 feet of waterline length.
If you make the boat shorter for its weight, it could still be a good offshore cruiser but it would not be a ‘modern day’ offshore cruiser. If you made a modern day design lighter and therefore shorter, it would eventually (somewhere greater than 30 feet) lack adequate carrying capacity to properly support its crew as a distance voyager, and fall back into a category that I would perhaps call a boat with passage making capabilities.
In any event, there are a lot of folks building decent boats with passage making capabilities, some of which are modern day designs. And there are still some folks building small long distance voyaging vessels. But I don’t know that anyone is building modern day, bluewater cruisers in the 25-30 foot range, nor do I believe that such is actually possible by the definitions above.
Respectfully,
Jeff