Now that we know Red has the Iron Bull power, making him a Red Bull, I think it's completely possible for those 2 to fight next arc. Not only did Germain steal his powers, he also insulted him. We alredy know Red is the type to hold a grudge. Even it it goes against Vlad's orders, I expect him to attack Germain, get injured and run away. Who knows, maybe he'll try more than once lol.
What about Gilles? We know Red Baron still sticks around Vlad, because of his daughter. Well, I actually think she would be ok with it. Tatsu made it pretty clear none of the Dragon Knights likes Germain, let alone someone who should be considered to be their elite. The recent Black Haircutter incident is most likely going to play a role here, since her powers, which were possibly given by Germain, caused quite a trouble as she lost control of herself.
Beating an alredy well established, dangerous character is a great way to showcase power. We have yet to see Germain actually fight against a proper opponent. (FTC was basically designed for a team battle). Besides, watching 2 villains fight each other is always cool.