The battle of Lake Trasimene 217 B.C. was Hannibal's second major battle in Italy but took the form of an ambush rather than a pitched battle. The army of Flaminius was ambushed on the shores of Lake Trasimene. The Romans were caught in march order and slaughter ensued with many thousands being driven to their doom in the lake. Following this, Hannibal's African troops were able to upgrade their arms to the best of the Roman ones.
Hannibal's army strength is unknown but it would not be much less than the 40,000 he had at Trebia where he had few casualties and those mostly from the Celts. I assume he was able to resupply from the Celts after such a handsome victory against their Roman oppressors.
We can re-use the Carthaginian order of battle from Trebia minus the elephants. What attrition amongst the men that may have occurred during the winter can be considered inconsequential for our units which are only approximations.
The troop ratio here is 150. While a ratio of 1:75 would work for the Romans and provide an army big enough for an 8 foot-wide table, this would be far too large for the Carthaginian forces to scale up to a 16 foot deployment.
Heavy Infantry - 9 units
4 standard African units (64)
2 standard Celt warbands (40)
3 standard Iberian units (48)
Light Infantry - 6 units
1 standard Ligurian unit (16)
2 African small units, skirmishers (16)
1 Moorish small unit, skirmishers (8)
1 Iberian small unit (8)
1 Balearic small unit, skirmishers (8)
Cavalry - 9 units
3 standard Celt units (36)
4 small Numidian units (24)
2 standard Iberian units (24)
24 units - 565 points
Lazenby argues that Flaminius would have found it hard to fit more than 25,000 men in the confines of the terrain at Trasimene. He assumes that there was a normal consular army of two legions plus allies.
The paper strength of a Republican legion was 4,200.
Total army strength was around 25,000 (Fabius Pictor):
Roman Legion I 4,200
Roman Legion III 4,200
Cavalry not fewer than 4,000 (Polybius)
Allies ~ 6,300 per wing
Employing a ratio of 1:150 to get us to one small unit of 8 models as the minimum infantry unit size means that :
Roman Legion I & III - 7 units
2 velites (16)
2 hastati (16)
2 principes (16)
1 triarii (8)
Ala Dextra & Ala Sinistra - 11 units
Cavalry - 4 units
1 Roman equites
3 Allied equites
22 units - 442 points
Since most of the Roman units are small this makes for a tough fight where they are vastly outnumbered, but due to the non-linear scaling of points to unit size in Hail Caesar the Roman force is only 78% of the points of the Carthaginians, provided the units are fielded with the typical stats rather than with the reduced stats suggested for Trebia on account of army fatigue and lack of brekkie.
This may make for a more competitive game rather than a simple exercise in sweeping Roman units into a watery end in Trasimene's waters.