What if C-3PO's and R2-D2's roles in Episode 1 were reversed? Would it make sense? You bet!
As we know, Threepio was a "side project" of the young Anakin Skywalker. A protocol droid he was building as a gift to his mom to help her out. A project that sounds sweet on paper, but really is just silly. R2 is an astromech droid that has the purpose of being the computer on a one man fighter (such as the X-Wing), or to repair damages on larger ships (Padme's royal ship). That make sense for him.
However, I have something that will make you want to make it your own head canon that works really well. Works way better than what Lucas gave us.
What if C-3PO was the "Royal Protocol Droid", and assigned to Padme from the get-go? First, it explains why we see Threepio always with Padme from Episode 2 on. He never wants to be with Anakin to go on adventures. He demonstrates a certain level of loyalty to Padme that should actually go towards Anakin if we consider the original context. With my version, it makes tremendous sense why the loyalty is towards her more specifically. It is his royal duty.
R2 could have been the droid that Anakin was building. Perhaps R2 was junked due to some accident or crash. The reason really isn't important. What is is that Anakin found the droid, and rebuilt him. Not only as a gift for his mom to help her out, but also to assist in building his podracer. In Episode 2 and 3, R2 shows some serious loyalty towards Anakin. Even in Episode 1, we see R2 attach to Anakin.
With this role reversal, it really don't alter the story much at all, and doesn't even require one to have to re-imagine many other scenes beyond their introductions. So, as I said...official head canon. This is what George Lucas should have done in the beginning.