High-elevation guns and long-range fire

What interwar naval development might have made the biggest difference without treaty limits?

Sustained work on high-elevation heavy guns and loading systems could have made long-range fire more effective.

Sustained interwar work on mountings could have given British and American heavy guns elevations above 45 degrees, with 55 degrees as a further goal. The benefit depended on the loading system as well as maximum elevation. A mounting able to load at about 30 degrees would spend less time lowering the barrel after a long-range shot. Those saved seconds could improve the rate of fire in a distant engagement.