customize drop down menu

No, you can'customize that menu and there is little chance this would be approved by Adobe. Saving as jpeg means you risk to lose some information about your work to save, and they don't want to be criticized on that account. However, so long as you are saving flattened files (only locked backgrounds), the jpg choice is sticky. So if you have layers for instance, flatten the layers before saving.

(Please somebody correct me if I am wrong).