When Augustus married Cleopatra Selene to Juba and granted them Numidia and Mauretania, could he have given them Egypt? What if he gave her brother, Alexander Helios, Egypt?
Egypt is too rich and populous to give it to a client king after it has become part of Rome. A scion of the Ptolemies is IMHO very unlikely to get any appointment in Egypt at all; after all they have an ancestral claim to the land and could easily cause problems for the Roman state.
I rather agree with @Pischinovski there : Lagid Egypt remained a client state up to Augustus because nobody really wanted an ambitious taking the control of the whole province and all its ressources, postponing its absorbtion within the Roman archê sine die. When Augustus got rid of his rivals, this caution became obsolete and the risk having a too powerful client king in Asia, possibly championing hellenism or regional causes, became the new priority.
Egypt is easily the wealthiest region of the empire. Judea and Mauretania are unimportant backwaters compared to the land on the banks of the Nile. I just can't see any Roman emperor giving the area independence.
Maybe with Ocatavian and Marc Anthony coming to an agreement you could have a Ptolemao-Antonian Egypt survive as a client state but after the downfall of Cleopatra and the outright annexation of Egypt there is little you can do.