Tele,
The code here is all Open source except those on the store, they have been reviewed by the dev's and then placed on the store for user safety & security. With that said, here are a couple things I am working on a couple public plugins and several private that are just for me. You can check my signature below for my tw public plugins.
Now, These are the following questions I follow when coming up with a plugin solution.
#1 What is the purpose of this plugin.
#2 Is there a plugin out there that does this already ( If yes answer 2a & 2b )
#2a What will this plugin do better and why ?
#2b Would it be better to request the additions/changes from the Dev than do it yourself.
#3 Will this plugin make other players lives easier ?
#4 How does this plugin interact with the environment ?
There are more questions, but honestly those should cover the main concerns, so write then down and then piece meal it together. I tend to write a demo application with the function I need happen, then add it piece meal it together.
Throw a thread up on the forums I suggest following the subject [Plugin] Name of your Plugin
Then describe your plugin and between the code tags provide your code.