I know these are your assumptions/opinion. Nothing wrong with that. However.
1. This has never been stated by the dev team. This might be the case early on, but going forward they have specifically stated that they want FFXIV jobs to be original.
2. This is [i]exactly[i] why Sage was chosen and developed. The dev team, and the Japanese in general are very symmetrical.
3. No, they're not.
4. I would say this is more true than an assumption. Anyone can come to this conclusion based on observation. In this case it would help to know where we are going in order to make job predictions.