I think you will find that the Alerion is not much more comfortable below than a J boat; it looks a lot better, but you can't stand up and the head is at best behind a curtain. I think you will also find that if you have an old sailor's soul, you can't help but fall in love with the looks of the Alerion. Unless you are a fan of the melted-cheese look of a say a Hunter or Beneteau (is my prejudice showing?), you will think the Alerion is simply the prettiest boat available today. Sure, the boat sails nicely, but it isn't the fastest, driest or most stately ride you can buy. You can buy a boat that is similarly styled; however, that boat will be about forty years old (and all that portends in terms of maintenance and problems) and have a full keel (and all that portends with respect to sailing performance). The point of the Alerion is that there is a niche market for those who want a classicly-styled daysailer without the headaches that come with buying a forty year old boat. You pay for the look. If I had the bucks, I'd be first in line. The Alerion fits your list because it is one of the few boats made today that is about the length you want that has an inboard engine.
The more you explain your needs, the more I see that some of your requirements work at cross purposes. You won't find too many "weekend cruisers" that have a separate head or an inboard engine. Need to single-hand? I would keep the boat to less than 28 feet; sail handling and docking a boat bigger than that alone gets too tricky for me. Privacy for the head: if you want more than a curtain, you will have trouble finding anything with a door under 27 feet. btw, this one issue more than any other drove me to pick my boat. After living with a portipotti behind a curtain for a summer, the Admiral insisted on a real door for the next boat. Inboard engine: very unusual to find in boats under 27 feet. Cabin adequate for overnighting? Adequate is a relative term, but if you are looking for standing headroom, you will have to go to 27 feet; less than that and the best you will do is with a pop-top model. Once you cross the line over 27 feet, you leave the world of weekend cruisers behind and enter into the realm of pocket cruisers. Here is what I can think of now: Some are pricey, but fortunately for you, that doesn't seem to be much of an issue. Pacific Seacraft made a couple of models that would work for you: the Flicka, and the Dana Point 24. The Flicka is a 21 foot ocean crossing capable cruising boat. The Dana Point is basically a larger version. both are very salty looking, full keel boats, but they seem to fit all of your criteria. They are also quite expensive, especially for their length. They are full-fledged cruisers, not weekend boats. both boats are out of active production, although I think they can be special ordered, and are generally available used. If you want to go used, there are some great older boats that used to qualify as full cruisers but would now be considered too small or uncomfortable to anything but weekend on. If you can find a well-restored model, any of these would fill the bill well: The Pearson Renegade: a 27 foot cruiser. One of the first production boats with the fin keel separated from the rudder. Well restored models go for around 10-15K. Pearson 26: a classic, but you would have to find one that has been retro-fitted with inboard power. I sailed on one 15 years ago, but haven't seen one since. I would guess that with an inboard, a nicely preserved P26 would go for around 10K. The Catalina 27 I think would also do nicely for you. If you are shopping without looking at the price tag, you can have a lot of fun!