As a C1 pro owner, working wifi would be nice. It needs to be way faster, so videos do not need to cache for minute to start and repeat it after 5 seconds. And this is the situation when it "works", about half of the time i get only thumbnails and videos just load for ever.
Live view on phone would help a lot when installing.
Background download for video files on phone app would be great. Who wants to stare a transfer bar for eternity, which is what it takes for just one file.
Glare is always a problem with dashcams, so do something about it.
If wifi could be fixed to stable and usable level, you can get rid of display and most buttons on the device itself.
Better optics for clearer picture.
Way to install to always on power supply, but detect when to sleep and not drain your battery. With this connection method, automatic connection to home wifi and working as a server, so i could check my videos while sitting at my computer. Automatic archiving when in home wifi, so that some crazy people could keep every meter of their travels without limitations of memory cards.
Higher framerate/bitrate for better motion handling.
Option for clean installation by power source with actual wires for 12v. I did connect my camera to cigar lighter leads, but inside the dash and with 12v --> usb ps from another source. There was always on voltage for interior lighting and that would have been closest and easiest source for 12v. Maybe we need to ask for car manufacturers to add usb sockets to mirrors, hoping that they do not realize they could add that whole camera and make aftermarket dashcam manufacturers obsolete. Umm.. Why would I hope for that, I'm a customer. There are always some gadgets that needs to be installed, so i need keep running wires behind interior panels for decades to come, now matter what 
