Oh dear! You've caught the "bicycle tinkering" disease. There's no cure so you might as well just go with it.

Whatever you're thinking about - just do it. I can pretty well guarantee that you won't be happy for very long with your first attempt or two and, when you do finally produce a bike that you're happy with, it will have cost more than an equivlent new one. On the other hand you will learn all kinds of things through the process and you will have the satisfaction of having done it yourself. Just think of the money as tuition in the "University of Bike Tinkering".

Have fun!