This is definately something that I've raised my eye about in FE. The leaders don't die. Why? They're on the battlefield. They are a unit. They should be able to die. It might really really suck for your leader to die.....but that's life.
I propose "succession planning" be implemented.
Let me explain.
Your leader has just fallen. Woe is your great nation. What ever will you do? Do you give up? Do you concede? Sure, that might be an option...but what if your more determined than that. What if you want your society to thrive. Why don't the people choose a new leader? One from the many champions that you've gathered along your journey??
Keep the injurys in place, but implement a % chance of death. If hit, a screen pops up informing you that your leader has fallen and that you are to:
1) Surrender (aka end game)
2) Choose a new leader
The new leader options will be those of the champions you've gathered so far.....or create a new champion. Yes, a NEW champion.
Pros and Cons to either option. The new champ, for example, will not be anywhere close in power to the champs you've collected along the way....however you get to detail his design.
Also....chance of civil war could be VERY nice.....if not REALLY hard.....to lose your leader AND half your empire....ouch. Maybe save this for insane difficulty.
Anyways, those are my thoughts....