If the "old rival" thing is referring to a returning Defense-Type user, then my guesses lean towards Wakiya or Phi as they seem like the most likely candidates in my eyes.
I mean no disrespect to Kensuke or Gwyn because I honestly really do like them as characters and would love to see them make a comeback too. But Kensuke (in the manga) had about as much relevance as Cuza (in the manga) did, namely none, and the Kerbeus line just kinda faded into the background with little to no effort in its stock combo.
With Gwyn, whilst he was a major character in GT and has more of a chance than Kensuke, Genesis' Infinite Lock System would make it difficult to translate into Sparking. So they would either have to, a). Make it one whole Layer just like Regalia Genesis and Big Bang Genesis, removing the Layer's customizability with the Chassis, b). Make a special Chassis and Chip that are free-spinning to emulate the gimmick, or c). Remove the Infinite Lock System entirely in order to make it customizable with other Sparking Layers.
With Wakiya and Phi, they're both major enough characters in the manga whilst with Wyvern and Phoenix, they're both beys that can translate into the Sparking System just fine IMO.
I mean no disrespect to Kensuke or Gwyn because I honestly really do like them as characters and would love to see them make a comeback too. But Kensuke (in the manga) had about as much relevance as Cuza (in the manga) did, namely none, and the Kerbeus line just kinda faded into the background with little to no effort in its stock combo.
With Gwyn, whilst he was a major character in GT and has more of a chance than Kensuke, Genesis' Infinite Lock System would make it difficult to translate into Sparking. So they would either have to, a). Make it one whole Layer just like Regalia Genesis and Big Bang Genesis, removing the Layer's customizability with the Chassis, b). Make a special Chassis and Chip that are free-spinning to emulate the gimmick, or c). Remove the Infinite Lock System entirely in order to make it customizable with other Sparking Layers.
With Wakiya and Phi, they're both major enough characters in the manga whilst with Wyvern and Phoenix, they're both beys that can translate into the Sparking System just fine IMO.