If you're interested in re-inventing wheels, don't stop at a new module that does something slightly different from an existing one. Noooo. Start with writing your own version of Perl. Too much work? Ok, so there's a limit then.

But maybe that's not your limit. ...maybe you want to create a new language. But first you get sidetracked on finding a better way to build a microprocessor. But as you start working on that, you realize that a new transistor design would be fantastic, and before you can do that, vacuum tubes should have been designed slightly differently for better longevity.

My point (that I'm making in a rediculous way) is that you can easily sidetrack a very good project by wasting vast quantities of time building specialized tools, when generalized tools would do the job just fine. NASA used to carry the "invent your own" philosophy to an extreme, and the result was $10,000 hammers, $30,000 toilet seats, etc. If you can ONLY accomplish your task with a $10,000 specialized type of hammer, you're going to have to innovate and make one. But if you can get the job done fairly well with a $15 hammer from the hardware store, you'll have some budget and time left to actually build the rest of the house.