Another idea I had was to keep the storyline mostly the same, except during the trip to Ohu, they stop at a farm. the farm itself is centered in my one shot and its here Wing ends up meeting his future mate. Though they are children at this point so Wing isn't really interested. But it's a little foreshadowing for the future. The whole thing with Ohu and Cross plays out the same except during the time when the villain come sot reclaim Mayu, he makes his threats known by sending a spy to infiltrate their ranks and kills a few. He then kidnaps Mina in order to draw Mayu out. This leads into Bat and Mayu going to rescue her and Cross goes after due to the small bond she forged with Mina. Meanwhile Wing and Kuro are being watched by their uncles Ken and George.
During this they fight with Mayu noticing how much Cross cares for Mina. I could go on but I would have to list it. Although mostly the same, it would have differences. For example, when they rest during their trip to Ohu, instead of Wing getting drunk, Mayu has a nightmare about Mao and wakes up and has a chat with Kuro. A sweet mother and son bonding exercise.
As for the villain. The best way to sum up his personality is he is insane yet calm at the same time. He keeps a cool demeanor and rarely shows his rage. He is all about respect and order and hates having his authority challenged. The pups he has brought in he has raised them to worship and idolize him. Mayu and Mao are exceptions. That's partially the reason he is so attracted to Mayu. She resists him and somehow he finds that strength interesting. Again, I could go on, but the quickest way to explain is he was heavily influenced by the Walking Dead villain "William Carver". Now he was a sick SOB, and he was one of those villains who you just wanted to die for his crimes.
Oh and on a random note, I just found out a group of Hungarian fans actually made a GNG musical. It actually was pretty good based on some of the clips, and a tad funny as the teenager to adult characters look like humans with dog ears, makeup and clothing (Riki himself wearing a badass long coat), while the puppies are portrayed as dolls. It's rather hilarious seeing the Cross actress carrying three dolls while the Ben actor looks on proudly.