Khr au where Skull and baby Tsuna live in Skulls airship full time. They get money for important goods from freelancing or having a small business, since they can fly they wouldn’t have to pay as much for shipping.
it’s already established that the Mafia doesn’t seem to pay as much attention to civilian businesses because they are civilian so it wouldn’t be hard for them to find a place in the civilian market without the Maifa realizing as long as they aren’t visible on the material and don’t use their full names.
This could lead to an interesting work where Tsuna slowly grows his guardian count as they go to live with them in the airship.
But it asks the question ... Why is baby Tsuna with Skull ? Most people wouldn't leave a cursed baby lookalike to care for a real baby . Maybe bribery and something in the will or documents , or Skull finding Tsuna alone with no adult in sight and thinking Tsuna either got disowned and kicked out of home or got orphaned .
Let's go with Skull finding Tsuna left alone (for multiple days) in the forest . And deciding then and then this is HIS kid .
And so Tsuna finds himself in the care of his new Papa (who's multiple times better than his previous Mama and Papa combined) and gets thought about life while traveling around the world . He's probably proficient in multiple languages .
And while traveling with his dad Tsuna probably gets into a whole lot of troubles , but at least it allows him to meet his Elements .
Like the time he got kidnapped and met his first Mist , Sun and Rain . While Tsuna was getting to know them Skull was creating trauma for the adults who dare 1) kidnap HIS child and 2) dare torture children in their so called "science" . The Mukuro Gang are in the shock of their life when Skull decides "If they are Tsuna's then they are HIS too" .
Maybe at some point they get Gokudera who actually swore loyalty to Tsuna and not the organization behind him(like in canon) . The amount of explosives he was allowed to carry will be lesser than in canon but make no mistake he is evenly if not more destructive than canon .
Then we have Tsuna who was allowed to develop into the even Sky/Cloud mix he was always supposed to be , and with Skull as the parent figure you just know he can be destructive enough to take down a city in the literal snap of his fingers but just chooses not to (not that it saves Reborn (if he even finds him) from being trow at least 3 towns away minimum)
The moment Reborn might try and find Tsuna he will be going on a hunt for red herring with how little information he has , and even and if he finds the kid he still has to find a way to get said child , his Elements and his parent (the literal strongest Cloud) to listen to him (he is getting buried alive)
The plot is in no better situation than Reborn
Xanxus is getting the seat of Don Vongola whether he likes it or not , along with the jewelry
Byakuran and Uni (and everyone other than the Mukuro gang in this universe) gets their ass handed to him for daring to hurt Tsuna's People !
Deamon gets exorcised by sheer spite because he dares to challenge any of those definitely crazy (and crazily competent) children .
The Rainbow arc gets solved by again sheer spite on Tsuna and his peoples part . Kawahara can be GOD as far as those very morally ambiguous teenagers are concerned and it won't stop them from beating his ass in a McDonald's parking lot at 3 AM on a school night , same goes for the Vindice . With the lesson of the whole Rainbow arc being "don't try and kill the only trusted adult capable of doing damage control of a group of highly destructive , anarchistic , morally ambiguous teenagers with lots of parental issues , unless you want to get killed in that case go full on "
Long story short , they all got forced to work together or else ...
As far as Skull is concerned if the kids are having fun anything goes