If he worships Urgathoa then the Shatter resolve feat from Faiths of Corruption is quite handy, any enemy that fails their save vs your channelled energy is shaken for a number of rounds equal to the number of dice the damage dealt (so two rounds in your case). This becomes even more powerfull when you remember that any shaken foe that is subject to another shaken effect becomes frightened instead. Going on from that, if you take the Quick Channel feat at 5th level then you can theoretically blast them for more damage than an equivalent fireball spell, and anybody still standing but failed both saves will be running for the hills!
If control of the undead is more what you're aiming for then I would suggest spell focus: necromancy as a prerequisite for the Undead Master feat at 5th level. With this you can add 4 levels to the hit die of undead you can control via the Command Undead feat, and increases your caster level by 4 for the Animate Dead spell.
Here is a quote from something I posted several months back. It's good advice - I just didn't want to type it all up again.
The archetype name you're looking for is Undead Lord.
It -is- a called companion, but it's not treated as a companion for anything. You can design a zombie or skeleton, and it just shambles around to fight for you. Doesn't gain feats, normally.
Now.. Go read Classic Horrors Revisted (namely the Walking Dead section) and the Bestiary sections on Skeleton and Zombie. Skeleton and zombie are templates. Variants exist, though if you do use a variant, you only are allowed half the HD that you would be (for the companion, it is equal to your HD regularly [so half for a variant]). You can use Skeleton Champions, which retain class levels, though they do lose some abilities, Zombie Lords, the zombie equivalent to skeleton champions, and plenty others. You might be interested in the Magus, which is a skeleton that retains its Intelligence and can cast spells.
There is a LOT of versatility if you look through all the rules. I designed a 14th level cleric who went Undead Lord. He had a minotaur skeleton champion who carried around a coffin on his back, which was linked to a demiplane with permanency on it where the cleric kept his undead horde to experiment on and junk. Battle starts, minotaur swings the coffin off and slams it down, then a bunch of different kind of undead stumble out (archery skeletons, magus skeletons, exploding zombies..). Without Leadership, I had an army. If I had taken that feat, it would have just been ridiculous. Necromancers are just plain dirty.
Never did get to play him.
I allowed the undead lord in my evil campaign to use a skeletal champion and it has worked out quite well (especially wrt roleplaying as it is his brother)
You're using UM to pick up the undead lord archetype anyways, you might as well try picking up Variant Channeling: Undeath.
It's pretty much Channel Negative Energy, but better. Not entirely sure if it would stack with Unlife healer from Undead lord at 8, but I can't see a reason it wouldn't by RAW as Channeling is a Supernatural Ability if I'm not mistaken.
Variant Skeletons
Numerous variant skeletons exist, such as those whose bones burn with an unending fire and those who drip with gore and reassemble themselves over time. Both of these variant skeletons can be created using animate dead, but they count as twice their normal number of Hit Dice per casting. Once controlled, they count normally against the controller's limit.
Perhaps the most dangerous variant skeleton, though, is the skeletal champion. This skeleton retains its intellect, and often any class levels it possessed in life. A skeletal champion cannot be created with animate dead—these potent undead only arise under rare conditions similar to those that cause the manifestation of ghosts or via rare and highly evil rituals.
Each of the following skeleton types modifies the base skeleton in a few key ways. Except as noted, these variations can be stacked with one another—it's possible to have a bloody burning skeletal champion.
Emphasis mine.
Now, if your GM simply doesn't want to allow it, you can't really argue that, but the skeletal champion -is- a variant.
I don't see the harm in it. My GM and I ran into the same issue, but ultimately decided it wouldn't hurt. Especially a melee skeletal champion - half HD is pretty painful.
The biggest threat of an Undead Lord lies within him utilizing ranged and casting skeletons effectively.