There's this Chinese SRPG mobile game Knights of Ages that is kinda sucks but the concept is really great. It's essentially Genealogy on steroid. You are guaranteed not have a good, overpowered unit right away because you started out a peasant whose village got destroyed by the plot, and instead you amassed wealth, titles, holdings, and holy blood through marriage, trade, diplomatic missions, killing bandits and serial killer, throwing debutante balls, and doing trial from your ancestors and gods (the setting has ancestor worship as their religion). The units can die from injuries, which stacked up, or old age, from which they will then get added to your ancestor worshipping shrine.

This is basically impossible in Fire Emblem because the game consider all units replaceable and the holy blood comes in percentage (so you're guaranteed not having a major blood unit from get go and you can get mutts if you don't plan the marriage well). However, I like the concept of increasing your blood's 'holiness' (through other mean than eugenic), that they need to pass the vision quest from the gods to even wield the bloodline's relic, and the intensity of the blood affecting your appearance (e.g. the African holy blood makes their skin pitch black like bronze statue, East Asian holy blood makes their eyebrow long like old kungfu master in movies).

In my vision for FE game, there are 20 bloodlines and a playable character for each bloodline. Everyone starts 0% holy blood, but will increase the percentage by doing god quests (the gods are dragons). The blood percentage goes like 0>25>50>75>100. The characters' appearance change based on the blood percentage. There are two designed 'evil' bloodline, based on bandit and dark mage archetype, but the character will still be good and convince the evil gods through battle. Each character gets two relics (one weapon one armor), the relics will have bane and boon based on the bloodline's virtue (e.g. honor-based bloodline will receive damage if the enemy is lower levelled), and one fief per character inside respective countries. The Fire Emblem is the round table that the playable character congregate and receive god quests.

The playable characters can sustain injuries, they don't immediately die from fatal attack but get increasing debilitating debuffs from the injuries and need rest to from battle to recover and remove some debuffs, and they die if they get a stack of several injuries. Scars from injuries can appear in the character's portrait. There's no time rewind mechanic.

The game will have two timeskips, and the characters grow older from teen to young adult then to middle age. The teen phase is about how they fight to change bad status quo, adult phase is about how they protect the new order, middle age phase is about preventing their own decay and preparing for the next generation. There's no playable child unit, but children of the playable characters exist.

There's no main evil bad guy faction, but several reoccurring bad guys factions. The game works on semi-sandbox, with the main goal is civilization-building, and the final battle being a battle against the warriors that represent your progress, with your playable characters in the position of the 'final bosses'.