Well, yes the eco system would break down because of nothing to eat. A CUC is simply a Clean Up Crew. Hermit craps, snails, and so on.
If you can't get a person to take care of your tank for you, like it needs to be taken care of, than yes it's best to break it down. However, if you want to keep the bio-colony strong and your tank running, ready for you to add fish when you get home. The method that might help is hanging uncooked shrimp in your tank.
Simply get some panty hoes (Clean of Course
), and put two or three uncooked shrimp into it. Hang it in your water (lower in your tank, so it will not get uncovered due to evaporation). This of course would mean your fish would no longer be in the tank. All your friend will have to do is replace the shrimp and panty hoes once a month until your back. Plus topping off your tank.
Also, with that method he/she would have to at least do a 50% water change when he/she changes out the shrimp and panty hoes (don't reuse the old panty hoes, it will be nasty!!). This method would basically be cycling your tank and giving the good Bactria something to eat. When you get back, you would want to do a 90% water change and test your water perimeters before adding fish again.
I am assuming you are using a Hang on the Back filter, or a canister? Everything would be running still as if your tank had fish. Just like it is now, the only difference there is no fish. Buy a cheap timer for your lights and let them run for at least five hours a day. The timer will more and likely get out of the time you set it, but it should keep the lights on for five hours all the time (meaning if you set it for 2pm to 7pm, when you get back the times might be 8pm to 1am). My timer moves times, and I got to reset it once a week.