if you dont wanna replace ike moves why not make the vader psa on ganon with nano vertex? there are already several sworded ganon psas and all that
Sorry this is a really long answer.
First of all, I don't want to get rid of Ganon any more than I want to get rid of Ike. The Brawl developers spent a lot of time designing, testing and balancing these characters. Something I've noticed about PSAs: unless they are amazing, people will use them once or twice, and as soon as they get over the fact that *insert name here* is in the game now, they go back to the characters they know and never play your PSA again. Yoda was a different story because I had a great idea for a unique character and the Smash designers didn't do a very good job on Metaknight anyway. When I imagine Darth Vader fighting in Brawl, all I see is a slightly slower and heavier Ike, just the kind of thing that people will try once and never use again.
Second, Ike's moveset with the force choke grab fits Darth Vader almost perfectly. (Warning: I'm about to go super nerd on you. Be prepared.) Anakin Skywalker was a practitioner of lightsaber Form V, called Djem So (no I'm not sure how to pronounce that). This lightsaber form is heavily based on brute force. The general philosophy is to make counter-attacks and overpower your opponent with incredibly strong lightsaber blows, using the force to enhance your strength (sound like a Smash Bros character to you?). After getting his armor, Vader had to adapt his fighting style to rely even more on brute force and precision.
Here's a quote from Wookieepedia: "The Djem So attack stance consisted of holding the lightsaber above the head, angled back and down at an approximately forty-five degree angle. The characteristic Djem So attack was dubbed the 'Falling Avalanche,' an overhand power blow that crashed down upon an opponent with exceptional force." Sound like Ike's smash to you?
Only a person as nerdy as me will understand without me explaining it, but Ike is basically Darth Vader already. No PSA necessary.