What about giving them a 2nd mage with 2 randoms , but no good research , no forgeboni , no good stats , no drainimmunity ?
Price 90-120 gold , not sacred .
They can be considered to be bought but are mainly only useful for some forging + some lowlvl summoning + some sitesearching .
On the other hand a spectre is exactly that anyways
So the only thing to improve them without changing the master smiths or adding a 2nd mage would be to make ulms troops really the best in the game .
One approach would be to give them non-capitol only blessable troops .
Another would be to make 1 or 2 elite warriors which are very expensive resourcewise , but equipped with e.g. rainbow armors or anything similiar to make them a bit tougher against the powerful airspells .