Hey you were on the right track.
It's just hard to plan the starting paths, because of how dramatically it reduces the cost of the bless. For example, one reason the Cyclops is so well liked, is because it is a fine SC, and also happens to start at 3E giving it a very economical cost for a major Earth bless.
The Agarthan mages tend to get some access to Fire as well, and with the prevalence of lava in the deeps, it sort of makes sense the Olm is familiar with this element as well. I really think that giving him 3E and at least 1 other starting path would make him start to look more attractive, if nothing else than as a bless chassis and high end caster.
If he were reimagined with 4 arms, I think that would be the most interesting way to make him SC capable, he does have a lot of little stubby limbs after all, so it's not too much of a stretch. There are other abilities that could be explored as well, perhaps regeneration (worms regrow!), or even an autocast of Darkness in combat (that might be a bit too powerful, but would be so cool).