...Intelligent Systems in 1990 expected us to replay og Shadow Dragon this much, huh. Ok, not as bad as Three Houses and maybe Fates (but those are literally different routes with their own narratives, so I guess my comparison is risky), but to find all these secrets you would definitely commit a little.
While yes, the large cast of characters in FE1/11 does give the game a lot of replayability, that wasn't
entirely their intention.
The game has a large cast of characters with a lot of overlap as a means of insurance; you lose one character, odds are you'll get someone, or already have someone that fulfils their role, albeit, slightly worse. This is precisely why the game has so many chapters where you gain multiple characters at once. For example: if you lost Cain, or Abel, by chapter 5, you'll already have 3 replacements for them in Hardin, Roshea, and Vyland. People like to meme about the Kaga games having large casts of mostly nobodies, but they forget that the games were intentionally designed around permadeath. You were encouraged to be flexible with your roster because they could die at any second. FE11 would go even further by implementing gaiden chapters that would only go to if you had 15 or less characters alive. Is it a completionist's worst nightmare? Yes, and even I think it's a little much, but, still, the intent was to view your army as expendable, but still give you an edge if you were losing characters.
Other games would experiment with this design philosophy. In FE4, while the cast may not be nearly as big, it still had some back up in the form of substitutes. By the end of chapter 5, if there were any characters that weren't paired up, or they died, their children would be replaced by substitute characters. Say Ayra didn't get married to anyone. Instead of starting with Larcei and Ulster in chapter 6, you'd get their substitutes: Creidne and Dalvin. Their stats are mostly identical, if not a bit worse, however, the main downside is they don't inherit inventory or skills like the regular child characters do. Most of them don't have Holy Blood either. There are exceptions, of course, you'll always get Seliph, and Leif, since their parents get married through the story. And you still have other non-child characters like Oifey, and Finn at your disposal as well.
FE5 would more or less force you to use different units with the fatigue system. If a character's fatigue exceeds their max HP, they'd be force to sit out for a chapter. This mechanic made it so that you'd have to carefully consider how you use your units. FE5 is another game with a large cast of "nobodies", but, again, it's for the sake of strategical depth, which I believe the game excels at.
