I'd say if you want a nice analog of that, look at OTL Pyrrhic War. Pyrrhus was every bit the general Alexander was (strategist is another matter, but both were roughly equal when it came to tactics). Their armies were constituted of roughly the same core of a Macedonian phanlanx with native tribes thrown in for additional support. Pyrrhus led from the front, just like Alexander, and could inspire his troops the same way Alexander could.
I believe that even Alexander had his limits. Even if he had lived, if he had tried to subjugate Rome (who, although busy conquering the Samnites during this period, was still a force to be reckoned with). The resilence of the Roman state saved them in the Pyrrhic War and I think that it would be the case again with the armies of Alexander. The Greeks were just too overextended. I don't think Alexander being at the front will work miracles by itself. Pyrrhus was the most celebrated general of his day, and he didn't fare very well in the long run.
Perhaps one thing Alexander does have in his favor, however, is that the most powerful city in Magna Graecia, Tarentum, is still at the zenith of its power, and not in the slow but inexorable decline it was in when it called upon Pyrrhus for aid.
Perhaps Alexander can pull it off. Pyrrhus nearly did.