I was always left with the impression that Shenlong originally just didn't grant the same wish twice. I don't think it was a matter of how much energy granting said wish took, as proven by bringing multiple groups back to life, just not people that had been brought back once, as per the original rule. For example, you could ask to bring Kuririn back to life but you couldn't ask the same thing again, even if included in a "bring x group of people back to life" kinda wish. Piccolo asked to be brought back to his youth, but the same wish can still be granted to someone else, (say...Pilaf lol) the same way someone other than Kuririn could still be brought back to life. Just not to Piccolo Daimao again. And no more panties, period.
As far as the creator of the Dragon Balls having the power to bring someone back to life....well...uhm....we do see God bringing Goku back from the world of the dead so, technically, one can say he can do it

(Although, I have to wonder what kind of agreements and paperwork with Enma this kinda stuff involves. Did Dende tune up the Dragon Balls and go "well, gotta head to Enma's and file these forms for future wishes under the usage of mystical items" ?

)
Polunga not being able to bring Goku back to Earth against his will gets a little awkward. We can make the arguement of that being the case because of Goku being stronger than Polunga's creator, but...pretty sure Vegeta didn't want to leave Namek before. And, speaking of Polunga, why was it necessary to bring Kuririn's soul to Earth? Wasn't his soul in the Other World? They should've been able to just say "Revive him HERE", right?