The only Nikons that can vary the aperture in live view are the Nikon. A hack done by nikon engineers to. Software tells it to, until live view.
It's no secret that you can hack Canon cameras firmware with 3rd party hackers like to push higher dynamic range and bitrate. Is looking to bring the same performance to their ecosystem. Their new set of hacks (for 11 cameras) allows you to push 1,080 video at up to 64mbps. While these hacks are still in beta, the results look promising. Their D7000 hack allows you to boost the stock bitrate of 24mbps to a whopping 64mbps. They also have hacks for the entry level D3100, D3200, D5100, and D5200 that allow all of them to output 54+mbps. Below is their list of available firmware patches along with the changes they'll bring. I've tried out the D7000 patch.
It works fine, it gives clean LCD display/HDMI out, but it's not switchable at the moment. When the patch is installed you get zero information overlay on the LCD/HDMI out, with no way to show anything on the rear screen other than the image, or menu screen. The only way to get the information overlay back is to reflash the firmware back to the original again. This isn't ideal, but it's a start. As for the increased bit rates.
I tried all of these with a pretty unscientific test clip and I personally couldn't see much improvement in quality over the original. I've been shooting with D7000s for a while and whilst there are some annoying limitations, no LV histogram, audio monitoring and having to switch out of LV to change aperture.
I'm still happy with the overall quality of the video I can get from it.