I like this idea, so I’m posting.
If small giant wants another option that has more random, they could do it trade up style (idea borrowed from cs:go trade-up contract).
Basically, consume 10 2* Ascension Item (possibly +resources, +time, +gems) yields random 3* ascension Item. Do the same with any inventory or hero:
consume 10 3* heroes, get 1 random 4* hero
consume 10 4* battle Items, get 1 random 4* battle item.
There may need to be some reclassification of * values, since scabbards and chainmail shirts shouldn’t be same level as fine gloves and hidden blades.
Levels:
1 uncommon Ingredients
2 uncommon battle Items
3 uncommon Ascension Items
4 uncommon troops
5 uncommon heroes
Add 5 more levels for rare ingredients, etc.