AOR systems, and the historical vs the realistic

[Arjos]

makes the idea that the Bosporans were somehow incompatible with Roman culture a bit ridiculous.

I didn't say they were incompatible, the opposite, since they were already hellenized, just had to accept roman overlordship, which they did...
Can't see them recruiting legionaries among the locals, that's all...

And the Rhine and Danube frontiers had exactly the same situation for centuries before the Limes collapsed, not to mention the eastern frontier with the Parthians/Sassanids.

The Rhine held until the situation changed; the Danube and the eastern frontiers were at constant war, with few diplomatic breaks, both sides coming and going in the other's territory...

Scotland, above the Antonine wall

That I didn't know, thanks...

A good example was the Legio V Alaudae, which was raised from the native population of Gaul in 52BC and was used to fight Vercingetorix during the Gallic Wars.

This I strongly disagree, both sides fought in a very similar manner, in the east and steppe it would be quite difficult and in a very limited number, actually more about whether the professional troops decide to side with Roma...