Well sure. Except one might as well make his fortune somewhere closer. You need to have a greater incentive to go the additional distance as it were. The Seleucids also seem to have provided free land, tax exemptions and grain subsidies. No word on the Baktrians.
The two were one and the same for about a century, so that seems very likely.
I'm not sure if "most" speakers of Western languages had to speak Latin though? I mean Greek was the administrative language of the East much as Latin was of the West and people still didn't take up Greek as much as Latin. Latin did also have some additional value as the language of the army. So there's that. But given how the Roman army was deployed; that would only explain uptake of Latin in recruiting areas or around military camps. As to the social movement mobility aspect, I agree. But that works mostly for elites and not for the hoi polloi. It's a complicated issue I guess.
Even ordinary people aspire to social mobility, though, even if only to be less lowly than their neighbours. Also, a large part of Roman ideology was the theoretical availability of the governor or even the emperor as a point of appeal in a dispute or against injustice; in many ways, it was what made the largely hands-off government preferable to what went before.
A Chinese observer recorded the practice (admittedly in rural Syria, but it's not a major stretch to imagine the same happening in the west) of the governor travelling from village to village accompanied by aides carrying bags, and urging anyone with a grievance to put a petition into the bags. There might have been nothing to stop him from throwing them over the next bridge and starting again,
but the possibility that he might read and deal with one's petition was a major part of provincial people's view of the state. In the same way, Russians during the Purges who tried desperately to contact Stalin and tell him what was going on, because if only he knew then he would sort it out. That sort of system allows people to see the state as a whole as benign even when their actual experience of life is grim. What matters for this point, though, is that in order to partake in this important part of life, you had to be able to write your petition down in a way that the (probably Italian) governor would understand.
I'm also not sure if there's much evidence of Latin derived Creoles developed in the West and I don't think development of a Creole language makes sense given that the factors you've identified as being important would tend to militate against it. One wouldn't learn a Creole Latin because Latin is a prestigious language that offers material benefits. You'd just learn Latin. The trickle down implied in your schema also supports this.
Yes, but probably provincial or dialected Latin, especially in terms of pronunciation. The very existence of the Romance languages lets you know that there were some differences between the way Latin was spoken in Italy, Spain and Gaul, and you can infer the same from the differences in English speech between Wales, England and South Africa. Does a sentence like 'No my never boyo, I never done that' not count as some kind of hybrid language?
In short, I'm just not sure what caused it nor am I convinced that the explanation lies in differences between Latin and Greek use. I guess if I were to offer another factor that we haven't considered: I'd point out that where Greek did expand i.e. Anatolia it had a much deeper population pool to draw on i.e. the Anatolian Coast. I think it also did well in Cyrenaica where it came to dominate the region. So maybe the relative size of the Greek population to the non-Greek population was an important consideration.
I think you're on to something there, but it's difficult to apply the same to the west because there's not such an easy divide between 'Roman' and 'native' - short of the residents of Rome itself and the immediate environs, nobody grew up surrounded by only Latin. Latin by its very nature was a common tongue among people who usually had their own local language, even within a few dozen miles of Rome. I certainly take your point that urban clusters (where interaction with the state is more common and the pressure for prestige usually more pronounced) help with the spread of language, but the West did have its fair share of those.
As a point of fact, by the way, the east was actually by far the most densely militarised part of the Roman world - the Sassanian front was the only border which the Romans were really prepared to fight along, Judea was one of the smallest provinces and yet hosted the most soldiers of all, and the general ratio of soldiers per unit area was massive. In the west it was quite unusual to see a soldier unless you lived close to the border or in Britain - that was part of the 'soft power' aspect of Roman rule, which tried to blend those within the empire into a common identity. What people often miss about the Roman use of force is that it was brutal, but part of the point was the provincials watching it wouldn't necessarily have been scared by it - their culture was reinforcing the idea that the people on the sharp end of it were barbarians (even
domestici hostes are always portrayed as such in art and literature; witness the Battle of Actium in Book VIII of the
Aeneid), so by inference they, as good, cultured Romans, had nothing to fear from it.
