I was thinking about this because of the opening credits of Voltron. "From days of long ago, comes a legend" What if Voltron was a tool of the Inner Senshi at a time when Earth was aligned with the moon before the start of the Silver Millennium?
Consider the lion colors and Senshi for a moment.
Blue, Mercury, water lion
Yellow, Venus, desert lion
Black, Earth (Tuxedo Kammen), power lion
Red, Mars, volcano lion
Green, Jupiter, woods lion
What if Voltron were a defender of the Earth Solar System that helped create the Silver Millennium but was sent out to the frontier because it was no longer needed at the heart of the empire?
What if the original breaking of Voltron wasn't because of a Space Goddess, nor Haggar's magics, but because of Earth declaring independence?
Supposing this is true what if Serenity was deliberately making it possible for her daughter and Endymion to become an item in hopes that finding the secret of Voltron again might have saved them from the fall of the silver millennium? The Enemy was combining Youma into a Super Youma after all and it was that combined might that even the Ginzuishou could not overcome without great sacrifice.
The idea is to have either Mamoron or another descendant of the Earth kingdom (Imagining a possible Ranma Crossover) lend their energy to the Senshi in a Sailor Planet Attack and have it manifest as the Blazing Sword striking down the enemies. That of course would lead to questions of what the heck caused that to happen and why. It also could lead to character development and ideas of visiting or restoring the planets castles to find the answers.
I think that the Lions appear to be dependent on their resting places in Voltron for recharge because they do not have the power link that originally made it invincible. Look how often Blue Lion gets mangled. But with Senshi Mana Taps in addition to how strongly built Voltron is... That is a pairing I could see giving Jurrai pirates(that have the full backing of Tsunami) pause.