The 3 trials to get to the Tribunal of Magic are actually the 3 trials that just about any fantasy hero would end up doing. The first trial is fighting against enemies. This is a trial of body — testing their physical skill in order to reach the next part. The second test is a test of mind — asking the Rangers if they were willing to do the hard work in order to save the world, rather than taking the easy way out? Finally, there's the test of spirit — would the Rangers fight on to help the world and make it better, even if they didn't have their powers? It's a pretty cool (if standard) progression of their quest all things considered.
The final scenes of the season show the humans of Briarwood accepting the magical creatures that inhabit the forest. This could potentially have helped sow the seeds for S.P.D., wherein humans and aliens live (mostly) together in harmony.
The Mystic Force Rangers become their Zords and grow giant sized rather than summon a robot (the 'cockpit' is just a visualization of the mental landscape of their fused form). This makes a lot of sense when you realize the Mystic Mother is a reformed Rita and she made the Mystic Force powers according to Word of God. IE, the Trope Namer for Make My Monster Grow.
In the "Dark Wish" 3-parter, Imperious captures Jenji and wishes that the Mystic Force Rangers never got their powers. The result is that history is rewritten: the villains, led by Imperious, conquered the world on the day that the rangers were supposed to get their powers (four months ago), and nobody remembers the pre-wish world besides the five rangers, Jenji, and most of the villans including Imperious. However, logically speaking, if the rangers never got their powers, Imperious and Jenji would still be trapped in the cave that only the rangers could open. Additionally, Morticon is absent from the post-wish world and would be alive if there were no rangers to kill him.