R3 brought one crucial change, which was doubling army movement and DRASTICALLY boosting naval movement. This significantly changes the strategy of KH in the early game, and with a few smart moves and heroic victories (and game engine exploits you can probably justify with roleplaying storytelling) you can control all of Hellas within 10 turns.
Turn 1
Have your diplomat in Hellas arrange an easy ceasefire with the invading Epeirotes... after they give you 2.5k mnai. Then have them dance around like a monkey and make animal noises. It works, trust me
Have your diplomat in Alexandreia sell map information to the Ptolemies for 300 mnai
Have your diplomat in Byzantion sell map information to the Getai for 300 mnai
Use the fleet in Alexandreia to move both FMs and hoplites from Rhodes to near Korinth. Then disband the two ships
Use the fleet in the Black Sea to move Areus and his elite infantry from Krete to near Korinth. Then disband the two ships
Coalesce all your FMs and heavy troops into a stack, flesh it out with Thessalian Cavalry, Hellenistic Cavalry, Scythian Archers, Cretan Archers and Mercenary Hoplites, and besiege Korinthos
Train one Classical Hoplite and one Elite Hoplite in Athens
Have your remaining light troops and cavalry wipe out the tiny Makedonian stack in Chalcis
Turn 2
Have your diplomat in Alexandreia travel to Rekem and sell map information to the Nabataeans for 300 mnai
Have your diplomat in Thracia travel to Skythiapolis and sell map information to the Sauromatae for 300 mnai
Have your diplomat in Hellas arrange another ceasefire in the wake of the scripted assault on Sparta by Kleonymes... after they pay you another 2.5k and you make the exiled Sparthan hoot like an owl in front of his troops
Conquer Korinthos and sack it
Kill the retreating Pyrrhos. Allow the disgraced Kleomynes to retreat back to Ambrakia
Move your uber stack to Demetrias along with your light troops from Chalcis and newly recruited hoplites, hire all remaining cavalry mercenaries, and besiege that settlement
Turn 3
Have your diplomat in Nabataea travel to Antiochea and sell map information to the Seleucids for 300 mnai
Have your diplomat in Skythia travel to Bosphorus and sell map information to the KB for 300 mnai
Antigonus will actually have recalled his army from Pella and try to relieve Demetrias on AI Makedon's turn 2. Defeat them all thus ending the Makedonians
Kleomynes, forced by the campaign script, will attempt to assault Sparta on AI Epeiros's turn 2, but having no siege equipment, will lose automatically
Take your uber-stack and besiege Pella, which is still controlled by Epeiros
Turn 4
Have your diplomat in Syria sell map information to the Hai for 300 mnai
Take Pella and defeat the spawned Celtic army near that settlement. Swing them back towards Thermon
Have your diplomat in Hellas arrange yet another cease with Kleomynes... for 2.5k again. Also make him wear a Spartan thigh-exposing dress and invite all his soldiers to spank him
Turn 5
Besiege Thermon. The roving stack will attempt to relieve the siege on AI Rebels turn 5. Defeat both and sack Thermon
Turn 6
Invade Epeiros, hiring as many mercenaries as possible, and besiege Ambrakia. An anti-decapitation army will spawn at the end of Epeiros turn 6
Turn 7
Defeat the relief force and occupy Ambrakia
Turn 8
Besiege Epidamnos. The roving stack will attempt to relieve the siege on AI Rebels's turn 8. Defeat both and occupy the settlement
Conclusion
With an extra 2 turns resulting from unforeseen incidents, you can confidently conquer all of Hellas in under 10 turns. Don't feel guilty about abusing the game engine. Just tell yourself that Kleomynes is very easy to convince, shelling over gobs of cash from the Epeirote treasury and degrading himself in front of his troops. It helps me sleep at night