How does that work? The two would appear to be mutually exclusive.
Doesn't mercy involve the suspension of justice? If God were even 1% merciful, how can he be 100% just?
Then wouldn't a 100% just God send us all to hell"
How is that 100% just?
If one man is required to suffer for the sins of all humanity, how is that 100% just?
You have hit the nail right on the head with respect to the Gospel and the Deity of Christ.
100% Just requires that 'the wages of sin are death' be paid to the last penny.
My sins (to avoid making this seem like an attack, but it applies to everyone else's sin as well) require a just God to sentence me to death.
If Jesus was a sinless man, then he might be willing and able to trade his life for my life ... to take the death sentence in my place.
If God forced the perfect human Jesus to die in my place, that would be 100% unjust.
However, the perfect human Jesus might reasonably have the right to take my place without being even a little unjust.
I would get 100% mercy from Jesus and God would get his 100% justice.
Perfect human Jesus gets royally shafted, but that might potentially be his right.
If nobody forced him into it, and he never changed his mind ... then a perfect man might have a right to die in my place.
In this imaginary exchange between perfect human Jesus, sinful Arthur and 100% just God ... I end up sitting pretty, and you end up screwed.
See, you have a debt of sin that must be paid too.
Unfortunately, there was only one perfect man, so as much as God might want to be 100% mercifull, that 100% just means that somebody must pay the wages of your sin, and only you are left to pay that debt.
Now just to mix things up a bit, let's assume that Jesus was still perfect, but he was more than human ... Let's call him perfect angel Jesus and let's assume that perfect angel Jesus has as much right to willingly die for another as perfect human Jesus did.
So how many human lives is an angel's life worth?
I have no idea.
Just for this discussion, let's say that each perfect angel Jesus is worth 100 human lives.
So now 100 sinful humans get to experience 100% mercy, God remains 100% just and the rest of humanity pay's their own sin debt.
Better, but that still sucks.
Now let's try one more 'what if'.
Suppose that God wanted to pay the debt himself.
Does God have the right to pay someone's sin debt?
Why not.
So what if perfect God-man Jesus decided to die to pay a human sin debt.
With the debt paid, God can remain 100% just.
With your and my debt paid, we get to see the 100% mercy of God.
The only question remaining is how much the life of one perfect God-man is worth in human lives.
As the creator of everything, the life of one creator is worth more than all of his creation.
Jesus Christ, the God-man, has the capability to pay all sin debt.
Debt paid, God stays 100% just.
Forgiveness available to all, God stays 100% mercifull.
Above all that, God gets to show off his 'perfect love' and by raising himself from the dead, God gets to display 100% awesome.
How is that for a plan?
Go God!