Nice Plan
I like @Noble_Weasel 's plan.
Duplicates
We probably will not have a definite answer for 6- 18 months.
If trade was introduced tomorrow, I have never seen anyone level more than 3x same 4* hero ( Grimm ) and 2x same 5* hero ( Gravemaker and Panther are famous ) but some heroes would command high trading value.
I finally reduced my Melendor clone army from 9 to 6 ( The lady running my training camps must have a crush on him, I have summoned him a lot more than 9 times )
4x 4* 1.1
1x 4* 3.60
1x 4* 4.70
Math
How boring do you want to get?
Yawn ( Spoiler 5* 2.60 > 3* 3.50 )
Yawn Yawn
Yawn Yawn Yawn
Emblems
Though emblems do make a 3*+19 hero roughly equal to a 4* 3.60 hero. So theoretically 3*+19 > 5* 2.60 but it gets very weird comparing emblemed heroes to non emblemed heroes.