Just because no other fighting game lets you tweak that means does not mean a new one shouldn't either. Advancements are made by trying new things and allowing for new ideas, especially in a franchise that's been around for a long time.
Not sure if you've played Halo, but that game would not nearly be as popular as it is if they didn't allow you to alter settings for Custom Games. Things like movement speed, jump height, player traits like always having Camo, etc.
In Smash, you know those matches you can play that are Lightning Mode, everyone with Bunny Hoods, giant battle, etc., well all I'm saying is let the PLAYERS be able to choose those things. If players want to create a Lightning Mode instead of Sakurai GIVING us a Lightning Mode, then why not? It would add so much depth to the game and would not take away from the core experience. Imagine if in Brawl players had the option to REMOVE tripping? It could only help the franchise and in Brawl's, it would have definitely been more respected, especially in the tourney scene if this were the case.
Yes, certainly, and giving players direct access to the physics engine and the ability to add/remove intrinsic parts of the game, without causing cataclysmic system crashes, would have only taken another year or so of development. It's ridiculous they didn't do it for Brawl.