This kind of third-party repository interface has been around for many years and in several different communities. I'm wondering if there's even software already to manage the infrastructure.
For example, for Python:
For Perl:
For TeX:
In hindsight it's amazing that something like this doesn't already exist for Arduino! I guess you can say the Wiki/Playground is there but it's time for The Next Generation.
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons