Been tempted to try them not as a bless-thug nation, but as a scales-heavy wannabe-MA Ulm. Now why would anybody want to be MA Ulm is of course another question
Anyway, they have many paths available. A rainbow pretender providing access to some death and astral opens up lots of more potential.
Early expansion is ridiculously easy. Grab a Sidhe champion and half a dozen Sidhe Warriors. Script the Sidhe Champion with Quickening Song, other spells*4, Attack rear (if he did have Flight as last script, he will fly right to the backs of the enemy). With that song you have quickened glamorous elite infantry, which will rip apart anything in their path. You can pump out such expansion parties each turn. Research will of course suck (as you have nobody researching unless you took an awake rainbow), but you don't need many such groups out there. Meanwhile the sucky starting army stays home to patrol. You'll have gold coming through your nose in no time, so should be easy to pump out at least three forts first year (and those Sidhe champions all can build temples and labs in the new forts).
Haven't really thought how to go on from that on. But you'll have a bunch of elite infantry with high MR, and soon some kick-butt buffs available. With any of luck the rainbow pretender should find something useful, and meanwhile Sidhe Lords become available in masses from all your forts.