[Balance] Fame + Heroes
In my current game I reached something like 1600 Fame to unlock my next Hero and it looks like the magical Hero slider went from the greatest Heroes back to the first group you can select from. I even chose Hannis, a hero I had already recruited. I'm not sure how the system works in general so I can't propose any amazing solutions. Unless you have the faction trait for quest maps you will have a very difficult time babysitting low level heroes during battles as the AI is smart enough to pick out the weakest members of your party (or at the very least randomly picking them occasionally) and OHKO them with a ranged weapon/spell/ability.
Perhaps as a way to rework the system so that you don't ever loop over back into weak heroes is to have the level of heroes you acquire through fame equal your sovereign's level. I realize this could potentially be abused by using tricks to over level your sovereign perhaps, but there are plenty of such tricks in complex single player games like this already.