If the problem with Neo-Spacians was that their inspiration was limited to 3-5 minutes a pop, then why did they choose it for an inspiration? They could have selected a relevant Tokusatsu show that DIDN’T have a time limit and then they wouldn’t have to poison the relevance of the PROTAGONIST’S ARCHETYPE just to remain faithful to the inspiration.
There is no more relevant Tokusatsu in Japan. Ultraman is THE Tokusatsu. And because like everyone designing YGO grew up on Ultraman, he's their guy. If you think Hero in Japan, you think Ultraman.
And they asked Kazuki and Hikokubo to design a new ace and gimmick since Elemental HERO was a bit played out by the end of Season 1.
Also the gimmick adds this thing called Dramatic Tension, which is good for writing and adds a heart pounding pulse.
And I mean, Elemental HERO wasn't really relevant until well into 5D's when the manga made the version you more generally know. HERO of both Season 1 and the Neos Deck were just generally kinda shit until things turned over.
But at the end of the day, dozens upon dozens of people signed off on this because it made for good TV.