Oh my, I had the same problem with Ness while using the Stage Expansion codes, P:M Balanced Ness for normal brawl made the game freeze after his entry, after I deleted it, it got back to work perfectly, however I do use the Deadpool PSA with Stage Expansion, but I use Gecko instead of Riivolution.
I don't know what caused that problem, but it seems that it's the exact same thing that is happening with you.
I think it's worth listing the codes I use:
-File Patch
-Extra slot for Alloys, WarioMan and GBowser
-Independent Pokemon Engine
-Separated Sheik and ZS Samus
-Toon Link has no Z-Air (I use Waluigi PSA)
-Tourney Settings(3 lifes,8min.)
-Unrestricted pause camera
-No invicibility upon respawn
-Independent Pokemon Engine V2
-Extra Stage Expansion