Should Eirika or Ephraim been a boss battle in Sacred Stones?

This might be a weird question, but I always wondered about Sacred Stones. Eirika and Ephraim, both of them throughout the story search for Sacred Stones. Twice their paths resulted in them reuniting. Together on the field they were unstoppable. But, I feel like in level 20 when Riev comes into play in Rausten, he should of taken the opposite twin of your choosing. Ex. Eirika story, you face Ephraim
Ephraim story you face Eirika.
I thought about this after playing Shadows of Valentia, since Sacred Stones and SOV, are a lot alike.
The twins thoughout the game find strength in each other. But, like SOV would it be like for them to fight amongst themselves.

As someone who started the series and loves this game to death… I can’t say that makes much sense given the plot. Despite the similarities of FE2 and FE8, they’re not the same characters. …And why Riev exactly? He’s not like Jedah at all. He’s a heretic priest who was cast out of Rausten for worshiping Fomortiis and attacks Rausten to destroy the last Sacred Stone (and to get revenge on Mansel). He does not have any control over others, he just can communicate and control monsters. Lyon if anything is closer, but even they are vastly different.

I say this as someone who likes my characters with a bit more hardship. By the point chp 20, both Ephraim and Eirika know who they are. They have liberated both Renais and Rausten and are now making their way to the forest. At this point the armies of Eirika and Ephraim are together. Nothing can stop them. Against high leveled monsters and Grado Remnants all that remain. It should be easy and it is. Thats what I am saying the final two chapters feel like something is missing. I also say Riev because he is supposedly the right hand of the Demon King.

You shouldn’t be putting your characters through strife just for the hell of it. Rather, try to think about how the challenge further develops the characters and/or how the situation might result from the character’s decisions. If it adds nothing other than trying to make the character’s life a bit more difficult or to contrive some sort of situation in which there’s a battle then don’t make the addition.

There isn’t any point to adding this plot unless you can come up with a situation in which Ephraim and Eirika have a genuine conflict of interest (which they don’t)