If you only need to test the hardware, then I don't think you need a Mer image. The stock raspbian is already availlable and contains the I2C driver. When it works, you can start to see how to do it with Mer.

One note however : the I2C driver by default is blacklisted, so you need to remove the line "blacklist i2c-bcm2708" from the file "/etc/modprobe.d/raspi-blacklist.conf".

Also, I am not sure about the availlability of the I2C_HID driver if you need it. Like in mer, you may have to backport/build it yourself.

I can't help more for now, as I have not yet played with its I2C bus, only SPI. The raspberrypi forums have a lot of posts about I2C so this can be a good source of examples.