Some things that could be investigated and changed:
Guns could indicate whether their is a bullet in the chamber (avoiding fatal accidents when the owner didn't know the gun was loaded). Guns could be designed not to fire if dropped. Guns could have trigger-locks and other child-proofing devices. Investigate where serial numbers are stamped (easy places for them to be changed by criminals?), and if each gun can be identified with certainty. Must bullets be sold that can pierce police armor? Investigate technology that would render guns unusable by anyone except their approved purchaser.
Some of these have been suggested, and gunmakers have refused. Every other consumer product has safety standards for its design. Guns should, too.