Help! ...transition between 3 states with client supplied transitions

Hi
I have an unusual problem and extra finicky client.
I have a 2D character with only 3 states ( and I assumed 3 different animation assets)

1- walking left
2- idle
3- walking right
At first I thought I would simply use a 1D Blend Tree and let Mecanim handle the transitions.
But the client insists on creating the transition animations as well!

So instead of the above I now have the following animation assets

1- walk left walk cycle
2- walk left to idle transition
3-idle to walk left transition
4- idle loop
5- idle to walk right transition
6- walk right to idle transition
7- walk right walk cycle

In order to seamlessly transition between each the current animation must play to the end as though they were videos.
Am I making sense?

I am a bit overwhelmed at the moment and have no idea how to proceed.
Can I still use Mecanim?

If not using Mecanim, how would I code the transition between states?

Any feedback appreciated!

 

Replied to the duplicated thread here -