I'm currently listening through Mike Duncans excellent History if Rome podcast, and I'm mulling over a few Pods.
1. what if Julia doesn't die, maintaining the marriage alliqce bwtween Caesar and Pompey?
2. What if Caesar was killed in Sullas Purges?
3. What if Caesar was defeated at dyrrachium?
4. What if Marcellus hadn't died of disease?
5. What if Nero or Argippa had died before Claudius, allowing Britannicus to inherit?
6. What if Boudicca had won the battle of Warming Street?
AND
7. What if Majorians fleet hadn't burned?
For my own thoughts, 1 means a radicaly different Civil War. Could we see Pompeys kid with Julia adopted in place of Augustus? 2 and 3 amount to the same thing, albeit under radically differenr cicumstances- the first means someone else becomes Dictator, probably- the Republics ills are far too entrenched via the Senate to really survive at this point. 3 means another Sulla period, but one which Pompeu is even more powerful- I can't see it ending well now that two strongmen in successive generations of romans.
4 means no Tiberius and probably no Caligula. Germanicus might get more support across the Rhine. 5 means a potentially lingrr lasting Juluo-Vlaudian dynasty. 7 means Nero probably abandons the province and probably is overthrown earlier. 7 means a potential Roman conquest of the Vandal kingdom, potentially allowing the Western Roman Empire to totter on for a bit longer.