I know, he tried to though and it didn't work, I've seen silver's story on youtube -_-
The fire blast would be a result of him not being able to merge with it, cause Iblis would've been too strong for him to contain it, thus Iblis would be unleashed rather than sealed away.
Then explain...where is Iblis coming from in relation to the attack? A random Iblis attack and he tries to merge with it and fails?
On the other final smash idea that Despero6 came up with, it is a decent idea, but what I was saying before was that the attack needs to fit the character. If you think about it, the final smashes each character does relates to them in some way. Bowser almost always turns into a gigantic monster, Mario's first power up was the fire flower, Luigi is negative because of always being 2nd best to his brother and would like to share the pain with everyone -shot-, and Peaches name speaks for itself. They do things related to stuff that fits them. I'm not saying dump his idea, I'm saying make it come a little closer to Silver instead of Shadow.