Haven't done so yet, but let's take a stab at it, shall we? (Methinks the reason it wasn't done initially is because the Ogre Mage doesn't have so many abilities to use as a base, but I'll use my imagination

)
1- +2 Climb
2- Power Attack
3- Strength +1
4- +1 NA
5- +1 to Initiative checks
6- Darkness 1/day
7- +2 Concentration
8- Invisibility 1/day
9- Charisma +1
10- Fly 1/day
11- Detached Limbs that are reattached reconnect within 1 hour, though decapitation still results in immediate death
12- Spell Resistance 2+HD
13- +2 Spot
14- Gaseous Form 1/day
15- Consitution +1
16- Powerful Build (as the half-ogre ability to count as Size Large sometimes)
17- Darkvision 30 ft
18- +1 NA
19- +2 Spellcraft
20- Flight (Su) as the Ogre Mage ability