[The Roman Empire reborn?]

I have a thought experiment for you.  What would it take to have the Roman Empire (or Republic) make a comeback?  What bare minimums would recreate a recognizable Roman Empire?  Here are a few I brainstormed:

1. Must contain city of Rome

2. Latin official language of government

3.  Roman Senate active

4. Army using Roman terms. Legion = division, Cohort = battalion, century = company.  Dux = 3-star general, etc

 

Further questions:

1. Would there be an official religion?  I don’t think there would have to be.  Maybe nominally Catholic in the west.  Tolerance for all faiths would probably be the law.

2.  Who would be considered a citizen?  Everyone?

3.  Would slavery exist?  It’s hard to imagine Rome without it but the point of this experiment, after all, is a modern Rome.

 

[How were armies raised outside of Rome?]

I have a question that I can never seem to find an answer to.

How, especially during the civil wars, were armies raised outside Rome?

For example, I read that Brutus and Pompey gathered an army in Greece to face off against Caesar.  What I want to know is where did those legionaries come from?  Were they living in Greece?  In a colonia?  Did they side with Brutus ideologically and travel from Italy to Greece?  Were they actually Greeks and not Romans at all?  If so, why would they get involved?