You definitely cannot eat and cleanse out the toxins with the lemon diet. Your stomach will always be upset. Please read the master cleanse book before you begin. It has a big tree on the front and it's free in pdf.
This cleanse is meant to be used as a juice fast and laxative-based colon detox. You want to use it differently. I have no idea if this works if you do it the way they suggest, though I can almost guarantee the cleanse has nothing to do with weight loss -- if you stop eating of course you'll lose weight. When you start eating again, unless you change your diet, you'll gain the weight back. Using laxatives can be helpful in a short-term fast, but they can also be tricky. I would think fasting by itself would accomplish as much as drinking lemonade. But if you aren't fasting, you're not doing the Master Cleanse at all, so what's the point? The real question for you is, what are you trying to accomplish? This fast program is mostly for cleaning the colon and for weight loss, so when you say you want to cleanse the body, what part of the body? There's certainly nothing wrong with drinking lemonade and taking cayenne, though obviously the maple syrup could be a problem because of the increased sugar intake if you're still eating your regular diet. So again, what part of your body are you trying to cleanse and why did you seek out this particular cleanse if you don't intend to follow the program?