Good solid points.

I often send the army for Caralis to Syracuse first. Many times, I can let the first wave of Scips take all the casualties while the Bruti take the city. That army (with a few mercs) can often re-embark and STILL reach caralis ahead of the Julii -- or at least in time to do the same thing I did in Sicily (let them start the siege, but YOU start the siege assault, let them bleed on the walls, but take the city for the profits yourself). I do this with one bireme (which NEVER has troops still on it at the end of a move after turn #2).
No douby about it just turtling and teching up can net the celts huge cash returns. then you build one great army with troops ready for garrison duty and you walk all over northern gaul. The isles are a real cashcow if you play it right with traderights.