So, this is about crossover that has been in my mind for sometime. It's a DB/Z/S and Naruto xover, where at his last moments Madara sends a part of his chakra which contains his memories and bits of personality to the dbz universe with his rinnesharingan's ability. That but then is transported to the hyperbolic time chamber when goku decides to visit it and exactly opens up near him and the chakra latched on to him which changes him slightly but drastically. The part of Madara's personality would fic fix the damage done by the accident during childhood while also retaining his personality and inluencing him with the shinobi mindset.
He would use the knowledge of the shinobi and learn ways to incorporate them with his Ki techniques and even other shinobis's like Naruto's Rasengan, raikages lightning armour etc (any other techniques are your choice ). He would learn the seals from Kami to use with his Zenkai boost ability ( blocking his energy so he can only use part of his Ki) ,resistance (for speed) Gravity seals( for stamina) etc. His ki would also become more versatile due to addition with Madara's chakra and be able to absorb and make the spirit bomb faster, while also giving him the watered down version of six paths regeneration that is in between six paths and Naruto regeneration almost like wolverine. He would have senjutsu skills as well.(you I wonder how powerful would a rasen-kamehameha would be.) He would also learn how to produce bio-electricity like the ssj2 and incorporate it with the lightning armour giving him a huge boost.(which should probably used to defeat frieza; see below for more)
He would also be asking about Kami' s heritage ( race,ships,planet etc) and about other gods so he visits King Kai and name,Yadart earlier. While with king Kai he would become curious about the system of gods and God ki (you decide how the system of Kai work) about G.O.D.s and how to sense God ki. He would also be more in tune with his ki to master and control it and master the Oozaru form. Optionally just Madara he would take in the DNA of Brolly (if he meets him in his (goku's) early space travel(learning about kami' s ship and all.) to make his super saiyan transformation easier ( if you with the S-cells theory As Brolly is already a super saiyan).Learning about wait and on name through their knowledge (after meeting brolly). He would learn about Frieza , vegeta etc. To be more knowledgeable and strong.
As such he will take various technology for the briefs2to study.
His love life, I think it would be more fitting to have him marry Bulma and ChiChi both and turning them into saiyans through the dragonballs and also adding A18 in the mix. Any other girl would be your choice. He will also not be that slow with girls and also learn seduction techniques with his ki either by memories of Madara or through some planet in space. And for him having extra wives use his memories of Madara to use it to increase his bloodline members or because of some last saiyan thing.
Goku will also purposefully limit his power with the seals to better him self and fight with other the fullest. Like he would be stronger than Vegeta but limit his power to around lower of him to win against vegeta with superior skills. With this he should always be powerful as 25% of frieaza with his 50% power locked. When he learns the super saiyan and God transformation is upto you but it must be before Namek. So that he can go out and win without problem. He would also keep his seals a secret as long as possible and only release his full power during DBS arcs.
Also optionally if you want to incorporate SSJ4 in this, I suggest you make it so that he has to master his super saiyan transformation and for it to happen he would have to master all SSJ , SSJ2, SSJ3 and remove the barriers between them to enter the perfect Super saiyan state (yeah sounds similar to cell.) which would look like his SSJG but be Good aura. The SSJ4 I would suggest making it as such that it is the prices of a saiyan achieving his ultimate Saiyan form I.e. Primal saiyan. which would like a trump card he would be saving for fighting his ultimate rivals like (Beerus,Jiren , vegeta etc). The Primal saiyan I would suggest be a state which once achieved would be like his permanent base form in which he can turn to his transformations more easily and use them better like the PSSJ ( NO ssj2 and 3s) god, blue.
I would also suggest to improve the time chamber, making use of it to make goku grow and age faster. If you want resurrect his parents that is alright as well. Or planet vegeta and use it as grand stage to shiw off his power. Against the acrosion/ice-jins. He later also used the dragonballs to resurrect frieza, cells, and evil buu then have them fight on a an uninhabitated planet and have the winner absorb the losers to form a new villain that is more powerful than the three combined and has a loooot more power for him to fight using his PSSJ and full seal release.
Also you have as much freedom as you like as long as the things are included. I don't think it's possible to incorporate everything yes, but you can change and mild situations to fully utilize the above suggestions as per your writing style and these are suggestions not rules (besides the early super Saiyan and also the multiple marriage in which Bulma and A18 are a must the rest are your choice) so be free to go wild. Like I said it's only an idea.
These are the barebones of the story that has been in my so if anybody wants to write this story the challenge has been issued. So either review or pm me if you want to take this challenge.