Not too many
After reviewing your criteria, I couldn't think of any boats that meet all of them. The one that comes closest: Oday 25: while the entire Oday line of trailer sailers all have the shoal keel/centerboard combo (early models of the 22 did not have a centerboard, only the stub keel) only the 25 is potentially big enough to have wheel steering added. However, you would have to overcome the fact that the rudder is mounted on the transom (how the heck do you get wheel steering on that?!). I have never seen a 25 with inboard power, but I have read posts on this site about owners who have added that feature to their 23's and 25's. Like most trailerables, the sailplan of the 25 is not particularly powerful, and it did not come with a traveler, although I have seen them added.I think you will have to make some compromises somewhere. The two most limiting factors in your criteria seems to be the centerboard/shoal keel and your desire for wheel steering. There just aren't too many boats built with the shoal keel/centerboard combination; it is perhaps the most expensive way to construct a trailerable boat. I agree with you if you are of the opinion that it is the best configuration for sailing ability in shoal areas and trailering; however, with the exception of the Rhodes 22, I don't know of any manufacturer of trailerables who is still making one. If you really want a trailerable, you may need to consider swing keel models like the Catalina 25, which had a tall rig option, came with a nifty sail handling package including a traveler, and was often retro-fitted with inboard power. Wheel steering is also going to be tough because every trailerable cruiser I know about has a transom-mounted rudder, and (even assuming you can find the room between the seats and reenforce the cockpit sole enough to accept a pedestal) there is just no easy or cheap way to retrofit that kind of system. To get wheel steering, you need to go with a rudder mounted with an internal rudder post; you may need to move out of the "trailerable" category of boats to find it. There are lots of great boats out there. Good luck and let us all know what you decide on.