-Ability to cancel something you've typed in wrong in a shell using the keyboard. Have you ever typed something in a shell, like a device name and made a mistake? The OS will pop up a requester saying Please insert volume xxxxx: in any drive" with a "Retry" or "Cancel" option. As best as I am aware there is no way to cancel that and return to the shell without lifting your hands off the keyboard and using the mouse to deal with it. If you could just press the ESC key on the keyboard it would save a huge amount of time...and not be an annoyance, and allow you to keep your hands on the keyboard. (if there is a way to cancel that requester via some existing keyboard short cut please inform me! Maybe I am clueless!)
Left Amiga-V for the left button and left Amiga-B for the right button in requesters. This has existed since the 1.x days.
-If there is any way to speed up iPrefs that would be great...takes about 1 minute to load a 1024x768 png backdrop on my 030 16Mhz...ouch. It can be even slow on a 060.
This is a datatype related thing. It just takes so long to decode that PNG with a 16MHz 030.. I suggest you convert your background picture to IFF, which is quick to load.
-Ability to display the Boot Menu in VGA only/DblPal/DblNTSC - maybe some keypress to toggle like they have for NTSC/PAL. Not sure if that is technically possible. AGA machines of course. Low priority.
This came along in 3.5 or 3.9 and also exists in the 3.1.4 bootmenu. The boot menu info texts tell you what to do to toggle between 15/31kHz modes. Probably hit space for PAL/NTSC and return for 15/31kHz.