Even if you don't use the game engine for a release you can still use the tools like MED or WED and export your creations to other engines to create old-school levels and 3d models.
Maybe you can create small gameplay ideas faster in Acknex to test them out before transitioning to another engine.
It might also be a good idea to check out the complete 120 AUM collection and Acknex Unlimited for game demos, examples and scripts. A lot of concepts and solutions can be transferred to modern engines. So you don't need to reinvent the wheel. So in that case you're right, there is a wealth of information.
And the most important part is, that you have fun.
