As terrible as it seems, I hope no Latin will escape Macedon. Either by the sword or indentured servitude while being settled. Make your enemies, your friends lol
I'm with you in spirit - crush all the Latins! However, odds are a "Flawless Victory" is pretty implausible. Seems likely that despite D3's best efforts a few small bands of Latin troops (especially cavalry) will escape the trap. That being said I expect that the vast majority of the Allied army to be killed or captured either at the walls of Thessaloniki or during their withdrawal back up Macedonia.
Also, how much of a shock will it be once Blucher and Co learn that their avenue of escape is closed off? I'd love to be a fly on the wall of their command tent once that bit of news comes in.