The reason I was going to have Mr. Thicknose as the GVG Zordon type that he has never left the valley, supposedly, and Grandpa Longneck has spent most of his life in the great beyond. & I was going to have that the GVG were not the first team, just that there hasn't been a team in a very long time.
How they get their powers is up to the gm, but my idea, as Ducky mentions in the Insane Cafe rp thread was the current guardian can transfer or bestow the power on folks who seem worthy or destiny seems to point to. Over time the team members 1 by 1 die, old age & other reasons, till only 1 is left, that last one is changed into a guardian. They basically do not age and wait till the time comes for a new team. As Ducky goes on to explain, as Mr. Thicknose was the last of his team, one of us will become the next guardian, eventually choose successors, and so on. That is just my idea, it may be totally changed and different for this rp.
If you'd rather have a stone it could be a small stone that each has hidden somewhere, a special cave they hid it in till it is needed again. Though how Grandpa Longneck had it and we didn't see it in the first movie, may need to go unexplained if this route is taken.
As for 4 footer weapons, some of those with a natural weapon as an adult maybe has them in their ranger form. Spike may have his spiked tail, and Cera her 3 full horns. For others, or maybe in additional, part of their costume may include a weapon, a sword, club, ect, on the end of their tail.
As for a rl more modern power rangers (or one set in the 80's, near future ect) I had started a thread but interest fizzled, I wish you luck and you may find it, or I can find the link if you'd rather, so you can look it over for ideas when and if you decide to start your own discussion thread.