I believe to keep balance and to possibly boost sales, a Legacy of Goku Super Game should happen separate from a Legacy of Goku 4, and I think LoG 4 should be a LoG collection, that way all problems in LoG1-3 can be addressed
Here is a more in depth idea list I had
*New 3-D graphics
*Voice actors for characters
*A choice between Kai or Faulcinor music on thr options menu
*Equipment and item system of Buu's Fury, but streamlined and more authentic to Dragon Ball
*Leveling system of Legacy of Goku 2
*Ability on the character switch/save pad to change what abilities a character uses
*Several new abilities and powerups for characters
*Revamped flight system
*All zones from Legacy of Goku 2 and Buu's Fury + new ones
*Old zones from LoG2 and BF redesigned to include flying mechanic
*Playable Characters (In order of accessability)
*Goku vs Piccolo in the 23rd Budokai Tenkaichi
*The Mount Kiwi and Annin quests after Goku and Chi Chi's wedding
*Dead Zone, Piccolo now playable
*Plays out like Legacy of Goku 1 except with newer mechanics implemented up until Raditz. Goku already knows Kamehameha and Solar Flare since the beginning of the Goku vs Piccolo fight, so the guy in the hut just gives you a useful item.
*The year period before the Saiyans coming has similar events and order and filler moments (Hell, Princess Snake, The Robot, collecting the Dragon Balls) and quests as in Attack of Saiyans. In the part where you train with Kami, only Krillin will be playable, as he is a playable character
*The fight with the Saiyans start with Gohan, Krillin, and Piccolo as playable. After the Saibaman fight, there will be a cutscene with the deaths of Tien and Chiaotzu. When Piccolo dies. The perspective shifts back to Goku where he goes through the events in Legacy of Goku, but with the new mechanics
*Goku vs Vegeta fight happens in a different location. After training under King Kai, Goku knows Spirit Bomb and Kaio-Ken (Which is like a faster paced SSJ)
*After that is done. There are two bonus sections Goku can fight before leaving for Namek. One is Dr. Wheelo’s Fortress, where Goku can fight Bio-Men (Reskins of Saibamen), and Ebifurya, Kishime, and Misokatsun as bosses. The main boss is Dr. Wheelo. This bonus part will not include the possessed Piccolo part as he is dead. The second one, again due to plot inconsistencies, is aganst Turles and his men. Goku will first fight through a gauntlet of Turles, Amond, Cacao, Daiz, and Rasin and Lakasei. The main boss here is Turles.
*Once Goku goes into his ship, the perspect shifts to Gohan and Krilling being playabe on Fake Namek and eventually the Real Namek. This part is entirely different, and would be more like Super Saiya Densetsu. Vegeta becomes playable after the fight with Zarbon, and you can play between Gohan, Krillin, and Vegeta they Reacoome. After Gohan loses against Reacoome. Goku becomes playable and fights against the Ginyus. When body-switched, Vegeta is playable to kill Jeice and beat up Ginyu. The fight with Frieza will involve the three again as Goku is waiting in the healing chamber. Piccolo becomes playable again in the middle of the fight with Second Form Frieza, and Goku will return in the fight with Fourth Form Frieza where it returns to being like Legacy of Goku with the new mechanics
*After this part is done, you get the ability to play a remake of Legacy of Goku 2.
*The first part is where Gohan, Krillin, and Piccolo are playable. It is the Garlic Jr Saga
*The three year training part has the first fight with Doore, Neiz, Sauza, and Cooler
*The 10 day gap between the Cell Games include more filler moments from Z, plus you can fight both Broly and Hatchiyack as bosses
*After Cell is beaten, Goku is unavaliable, but Gohan can go Super Saiyan 3
*The Buu’s Fury arc is pretty much identical but with the new mechanics.
*A bonus boss is accessible, Hirudegarn
*After Hirudegarn is beaten, and all the Hercule and Z items are found, the Hyperbolic Time Chamber is acessable again where one can fight through waves of every boss in Dragon Ball Legacy of Goku with modified stats, after all is beated, some special feature is unlocked (Got lazy here)