Kegan you should identify who this is for the reader pointed out that he suffered from two things that were truly detrimental to him, alcoholism and uncontrollable temper. With these being found it appears that the illness could have saved his image. Those two key personality traits tying into the last years of his life would have put him into a similar deadly equation rivaling that of Julies Caesar.
First to start, looking back into his past Alexander has a night spent in a drunken rage where he actually kills his good friend and revered general Clitus. In order to suppress the uprising and threats on his life stemming from this man-slaughter, he has to kill another seven Macedonian and Greek leaders. This incident alone points to an issue that could alone cause self destruction.
Jumping ahead towards the end of his life, whale he is at opus his army has a munity, with how over worked his armies were and stretched out his empire became, it would be easy to make the conclusion that Alexander was at the very top of what he was capable or reaching and teetering on the edge of an empire collapse. All those parts make it easy to conclude that had he lived past the malaria, he would have then seen his empire fall apart as it had when he died. It wouldn’t even be too far to say that he would then end up like Julius Caesar himself and get assassinated. Even though many speculate that is exactly what happened to him.
Therefore saying that had he lived another thirty years it would just mean that he would get to watch all that...