I dont know if slingers count as skirmishers but, in my Casse campaign I disbanded all my army and boats after sending my diplomat to get trade routes. Then I waited a few years till I had about 8 or 9k in the treasury. Then I decided to make a bunch of slingers and see if I could conquer Britain. With a single full stack of slingers and my generals chariots I pacified the whole place in about ten years. They do pretty well in close combat after gaining some exp.