The next stage after the cat5 bridge is to add P82B96 buffers on the i2c lines and a level converter. This will add some more resilience and make possible longer runs of i2c cables.

references

http://www.ti.com/lit/ds/symlink/p82b96.pdf

https://pidome.wordpress.com/manual-howtos/pidome-hardware/i%C2%B2c-bus-extender-for-the-raspberry-pi/