The theory is sound
You've got to be prepared for the fact that 2nd hand parts sales are pretty slow right now, and though some items off the bike may sell instantly, others may take weeks or months. That and have you got your valuations accurate? What if you only got £600-700 for the parts, not the £800-900 you want? Would you be upset or could you live with it?
Just playing devils advocate here by the way. I've done this sort of thing continually over the last 10 years or more, and more often than not things have worked out well for me. I have been stuck with a few items I just seemingly couldn't shift for love not money, despite supposedly being desirable and in good condition, on occasion.
Oh, and Royal Fail charge more than ever, and they don't like funny shaped packages such as MTB handlebars very much for instance!