With the new setup I plan to implement with ribbon cable and clips, the total length of the I2C bus wiring should not exceed 2.5m. I don't have to use a Mega, I just already happen to have it mounted with a screw terminal shield, so using a level shifter seemed like a better solution. Also, the Mega features 4 interrupt pins (technically 6 but I'm using 2 for I2C) as opposed to the Uno's 2, which would not suffice for my particular project.