Whats the most effective way to balance tire clearance and bottom bracket drop in a gravel bike build, considering the increasing popularity of 700x45c and 700x50c tires, and how do manufacturers and custom builders reconcile the need for increased clearance with the potential drawbacks of a higher bottom bracket and reduced stability, especially when it comes to maintaining a responsive and agile handling characteristic in technical terrain, and are there any emerging trends or innovative solutions that could potentially redefine the conventional wisdom surrounding gravel bike geometry and design.