@Aurélien-Fi At the end of the day, the MT7688 chip in the Omega2 is really targeted in in a router, access point, or similar. It's good at connectivity (Wifi AP and client, ethernet), but not at things like cameras or displays.
The chip in a Raspberry Pi is the opposite - note that a Pi Zero doesn't have any way to connect Ethernet, but has HDMI, a camera interface, and USB device support.
My point here is that different processors have built-in hardware support that will make some things easier than others. The Pi Cameras are only so cheap because of the dedicated hardware in Pi.
So, this isn't something the Omega2 will be really great at doing. That said, there are ways. The main issue is one of bandwidth - I2C isn't that fast, so I'd look at SPI, UART, or especially USB. I think the Omega2S even breaks out PCIe, which opens lots of possibilities.
The little Arduinos don't have much connectivity for cameras either, so solutions for them might work out. For example: http://www.arducam.com/arducam-mini-released/