The real thing is, would Ging have bothered to appear had he known Gon was walking around town freely? No I don't think so. Ging has said many times that he does not want to meet Gon, suddenly when Gon seemingly has no way to meet him, Ging is at ease and freely moving within the same city as him. Ging wouldn't come to the Zodiac if he knew there was a chance of Gon running into him. I'm guessing he thought he could get in and solve things with the Election before Gon got healed.
How is Alluka too convenient? She is hardly Dragonballs as she has a major drawback and her life is constantly in danger. Her ability has a restriction, a very specific one, only Killua can use it freely, everyone else must suffer severe consequences. This is an unconscious vow that she has placed upon her inherent nen ability. It makes sense and works within the structure of nen that Togashi has created. Some say that Killua doesnt have to pay a price to use Alluka's power, yes he does, the price of having to constantly protect her from those who seek to use her. She is constantly living in danger, there is no way that is convenient at all both literally and plot-wise.
Let's say Goku arrived to take care of Pitou during the Ant arc so none of the transformation stuff was ever needed. The Election arc still would've happened. Pariston would still do exactly the same thing. Now we know people can't just randomly barge in the room the Zodiacs are meeting at, so Ging doesn't necessarily have to meet Gon right away, though we should expect to see Mr. Panda more often as a precaution. Hisoka missed meeting Ging during the vote casting period, so Ging could even be really fast to avoid being spotted there too.
But there are two major All-Hunter gatherings he has to be present (the one Leorio punched him, and the final voting round). Are you saying if Gon was perfectly alive and fine then Ging would've hid himself during those two crucial gatherings where he must be present? That'd give Pariston free reign to do whatever he wants, and remember at that point, not even Ging really knew Pariston had planned. Given how much the rest of the Zodiac feared Pariston, it wouldn't be a stretch to say if Ging wasn't present maybe everyone just gets killed by Pariston somehow. Is Ging willing to take that much of a risk just to avoid seeing his son? Because if not, then he sure isn't going to be avoiding him and I'd hope Ging cared enough about the association to stick around in the two crucial gatherings.
There's no point to talk about the 'pay 3 demands back' version of Alluka because that wasn't the version that saved Gon anyway. We can assume this is because there is probably no way to actually do the consequent 3 demands had such a wish been used. That version is reasonable but it wasn't the one used, so it's not relevent.
For the freebie version of Alluka, the notion that this power has a weakness is absurd. The first wish Killua can make is 'Constantly banish anyone with ill will toward Alluka or me." In fact, this wish would just be a combination of being able to read people's thoughts (Pakunoda can do this) plus a Banish effect (Razor can do this, at least in a limited form). Since Alluka's is capable of doing things nobody can possibly do in HXH, using a power that is just a combination of existing power is trivial. Once this wish is established nobody can possibly harm Killua or Alulka, he then has all the time he needs to figure out what to do. He can erase people's memory if needed, or change people's personality, or whatever he deems necessary to get the job done. Yes I get that there's this whole bit about how he doesn't want to take advantage of his free wishes, but surely he is aware that Ilumi was going to try to control him to get free wishes. Why would he need to be afraid of this when he can simply wish for "Make everyone besides me who knew about Alluka's power forget Alluka has such a power?" Is one selfish wish worse than just letting Ilumi control Killua and make as many selfish wish as he wants?
There are also many variants like 'teleport Alluka and I to middle of nowhere", and then teleport Gon to him for example, and nobody would be able to track them. He can also just wish to become the strongest guy in HXH and then he'd have nothing to fear from Ilumi. And keep in mind he was already planning on using a free wish anyway to cure Gon, because it seems to be heavily implied that there was no way Killua could've repaid the price for curing Gon the standard way (otherwise he should've done that, if the goal is not to abuse any wishes). He ended up using quite a few free wishes anyway, so it's not like he's refusing to use it at all costs, so why not just start with a wish that definitely gets the job done?
---------- Post added at 12:46 AM ---------- Previous post was at 12:35 AM ----------
As an aside a long time ago there was a really good 'fake info' that has a confrontation between Ilumi and Killua over Alluka, and Ilumi says something along these lines:
"You say you want to protect Alluka from our selfish wishes, but it is you who make the most number of selfish wishes! I told you that you do not have the rights to have a friend, and likewise you do not have the rights to Alluka!"
If you think about it, Killua must have experimented with Alluka's power. How does he know Alluka can teleport others if he didn't try it before? If he tried to teleport Ilumi away and it didn't work, then Ilumi would immediately try to subdue him and then get his infinite wishes if he succeeded, so he's taking a huge amount of risk and he must have known ahead of time that Alluka can teleport others. Even at the very end, his wish was that Nanika only fulfill HIS wishes. I always thought it'd make far more sense if Killua's limitation on wishes is because he feels guilt from abusing this power more than anyone else, but that's obviously not what happened.