The current version of Alchemy4Tridion (0.6.0) currently only packages the plugin's actual DLL into the
.a4t package. We're working on some ideas for a dependency system for 3rd party DLLs to be configured to be packaged as well, without causing issues if two separate plugins use 3rd party libraries of different versions.
The current workarounds (2 of which you found) are
- deploy the 3rd party library to the GAC
- deploy the library to the plugin's
- deploy the library to the Alchemy
Options one and three are probably the easiest if you are in development mode and doing a lot of uninstall/reinstall of your plugin as you test.
An experimental system for third party libraries may be released shortly, if/when it does I'll update this answer with a how to.
Hope that helps!
The functionality to add 3rd party DLL's to plugins has been added with the release of 0.8.1. A how to article can be found at http://www.alchemywebstore.com/help/how-to/Packaging-DLL-References.