This is a very good base for many ideas in fact. You could make Fame a real resource instead of just a "counter till something interesting happens"
1. Spend fame for Hero xp.
2. Spend fame as maintence on pop/production related spells (i.e. a stronger version of Sovereigns call, 2 fame a turn cost gives 3 pop).
3. Spending fame for henchmen is already in.
4. Spend it on "Celebrations" aka random positive mid-duration empire events.
5. Spend fame to buy trait points(like 200 fame a point)
6. Spend it to Cast Quest or rare spells - Call Legendary hero(summon an overstated hero, limit 1 per customer)
7. Use it to incorporate more Faction specific/special buildings - 50 fame, 10 turn build or cast and you could get 1 shard of your choice in a city, limit 1 per faction
If we switch mental gears and instead of thinking about fame as a "Count" like prestige, and instead make it production resource but on the Empire level there are many interesting things that can be done.