A liquid fast like you're talking about would send me to the hospital within days. I'm thin and need food to function. Not sure that your theory behind fasting is the best either. By drinking only liquids you're essentially shutting down your gut - yes, this will allow it to heal because it's not having to work. But, by not having it work, when you do start to eat solid foods again it would seem to me that it could only aggravate things all the more.
The worst flare-ups I ever have is after the colon prep for a scope. It takes me a good month to get back to being able to eat even relatively 'normally' again.
Why not resort to the BRAT diet when you're flaring. It provides nutrients, keeps your gut working, but not overworking, and seems a little safer. Or, try a low-residue diet - white and light I like to call it.
It's your call, though, you know your body best. But, for me, just thinking about a liquid diet makes me goosey.