Right your suggestion are kinda hard...
Can you make the explosion last longer? just a little bit about 0.1-0.3s is okay.
- I had to control the particle count. Currently the effect itself already has high particle amount. Think about an old computer had to face 20 of these at the same time. Probably would lag. So, its a no.
Secondly, make the cracks darker in order to make people thing that they are deeper.
- The cracks are actually default Blizzard-made image. Which means the patterns, saturation, brightness etc are actually by default (Unchangeable unless you edit the image themself and replace in map). It is possible to make the cracks darker, which by doubling the current amount of crater displayed. But then it would add up filesize, looks weird and to be honest Im not in much motivation to do so.
One more thing create a hole when the meteor finish its land and make it last longer than the cracks one second. (because your model is not a meteor strike it is just a fireball hit the land with great speed, the damage it make is too weak to be called meteor)
- Hole? I think you can achieve such thing with triggers. Also, I do not know how to do so unless you teach me.