[Knai]

EA Arco is my favorite nation personally, even if they aren't hugely powerful. They lack some of the fun parts that MA and LA can pull of easily, but there are some advantages, and some ways to have a lot of fun. Oreid assassination is always entertaining, particularly once you have high Thaum research and just Charm the guy, which works very well against SCs that aren't yet outfitted with all the MR they will be getting later but still good enough to hurt people.

As for Arco builds, I've used no Sloth builds before, some of which work well. The hysapsist is a nice little unit to mass, and in EA there is fun to be had with the Myrmidon, and a high production build might actually be able to use Wind Riders, and they can be useful, though they are overpriced.