Problem is those are books. They are written by great programmers, but the problems are mostly toys - useful elegant examples, but the longest in SICP is still only a couple pages long. Sure it is cool they implemented SCHEME in a couple pages (you can tell how old the edition I have is), but if you wanted a real SCHEME implementation it would be much longer since you will want to spend a lot of time on optimization. If you want your SCHEME to be used it needs to have a standard library so that you don't have to write sort, trees, and all the other things we expect from a useful language. If you want this done in a reasonable amount of time you will need multiple programmers and in turn nobody will understand the full and so there will be some code that isnt' elegant.