So I always thought about how the invasion of Persia would go differently had Phillip invaded rather than Alexander (lets assume he doesn't get assassinated until after he finishes his war, since it seems like he was pretty much destined to be assassinated at some point). I feel he certainly has the military ability to go as far as Alexander did, but the foolhardiness or boldness to do it, given the enormous risks involved. An interesting thought would be if, assuming he achieved a level of success early on similar to Alexander, he accepted a similar proposal from Darius that Alexander turned down: all territory east of the Euphrates a very large payment, and marriage to Darius' daughter. That would seem like something he'd be willing to accept.
Alternatively, I could only see the maximum extent he'd be willing to go being Ekbatana and Susa (and possibly Persepolis). There wouldn't be much reason for him to chase Darius and Bessus into the desolate mountains of Baktria and Sogdiana (and there wasn't really for Alexander other than to claim more territory and try and capture Darius and usurp his throne), and it would make more sense to consolidate by that point at the latest.
What do you guys think?