No, dude.
The travel time between, say, Rome and Carthage in the olden times was about
4 days (worked out using this:
http://orbis.stanford.edu/, which is awesome as hell). Rome could send a proposal to Carthage and have a response in just over a week. The shortest period of time ever covered by a turn in a Total War game is
3 months (four turns per year).
There is
no realism in personally having to recruit and move around your diplomats in your role as Emperor, Consul, King &c or whatever you are. Diplomats were, dumb, stupid, rubbish and basically all negative adjectives in the english language and getting ride of them was one of CAs best ever decisions.
The only thing you get from them that you don't get from the current system is the ability to have diplomats with different skill levels and characteristics (e.g. this dude hates greeks. don't send him to propose a treaty to the greeks) but this was crap in Rome and Medieval 2 because:
1) the AI just refused everything you offered anyway
2) Like a lot of stuff back then, there was basically no feedback through the UI so you had no idea if your proposal was rejected because they were going to reject it anyway (see 1) or because the guy you sent was a massive dick.
If they wanted to do that from Rome 2, they can still do it by abstracting it in the same way they did for government people in Empire - "Here's a list of diplomats - pick one to go and treat with Pontus" and it would be pretty cool because they've learned that giving feedback is important in making game mechanics feel worthwhile and also that there's no point in diplomacy if they AI won't use it.