Well…this is way harder than I actually expected. After many failures trying to use some crazy shader or blend shapes techniques, I manage to create something that I can work on.
Thanks to a Steven Craeynest post https://stevencraeynest.wordpress.com/2013/03/29/easy-volumetric-explosion-in-unity3d/ I got the path on how to do this kind of thing; however, tweaking the shader he creates there didnt get me the results I wanted so I created something based on that from scratch on amplify.
Im using a high division sphere mesh, and the shader, using a control texture, where the red chanel serves as displacement for vertex , green for clipping mask, and blue adss and extra layer to the clipping mask with that granular dissolve. The red channel its also used for color replacement, using a color gradient texture.
Then, to control everything, I use data from the vertex colors, so I can create the transitions from the particle system component; Alpha VC is used for displacement intensity and color replacement gradient offset, and blue VC controls the opacity mask.
I´m not entirely happy about how close to the reference this would allow me to get, but from now It´s the best I´ve achieved.
Next steps are tweaking the colors to get closer to reference and create the correct explosion behaviour, I also think I could use some emission on the shader so I would try adding it.