I did remembered that back at Super Smash Bros. Melee that Marth and Roy didn't have a Stage available, while Castle Siege that is from Daein is the truely first Fire Emblem stage in SSB series that appeared in Brawl and later that we got Arena Ferox from Ylisse and Coliseum (possibly from one of the Fire Emblem Arenas) in Super Smash Bros. for Nintendo 3DS / Wii U (but when Corrin was added in that he/she became the third Fire Emblem rep that to not receive his/her own stage based off from his/her continent and the only DLC newcomer in For Nintendo 3DS / Wii U to not receive his/her own stage as well) and finally when Byleth came in Ultimate that comes with Garreg Mach Monastery.
I do remembered that the development back in Melee that Marth and Roy were originally going to have Archanea stage planned before it became scrapped and Elibe stage was never been mentioned in the works in Melee (presumably that I think Elibe stage wasn't planned to exist since Roy was existed around 1 year before his first canonical debut in Fire Emblem: The Binding Blade at 2002).
If Marth had an Archanea stage, Roy has an Elibe stage, and Corrin has his/her own stage based off from his/her unnamed continent. Which of the three stages based around in the locations do you think it would fit in Marth's, Roy's, and Corrin's own stage? I was thinking Marth's would might be around a battlefield somewhere in Dohlr, Roy's might be somewhere in Pherae, and Corrin's stage would might be a traveling stage to travel to Nohr and Hoshido similar to like Delfino Plaza, Prism Tower, and Garreg Mach Monastery.