Abilities and NA seem the natural next choice.
The Pentadrone has Str 22, Dex 12, Con — in
Dragon Magazine #354 and Str 18, Dex 16, Con 14 in the WotC website's
Manual of the Planes Web Enhancement.
How about Str 18, Dex 12, Con 14 for our boy?
Although I'd contemplate going a bit higher and maybe making the Dexterity 14 instead.
Constitution 14 would give it 45 hit points.
For the Mental abilities, I was thinking 10s across the board, which'd make it:
Abilities: Str 18, Dex 12 or 14, Con 14, Int 10, Wis 10, Cha 10
That's all even abilities rather than half-odd and half-even, so we could mix it up a bit and give it odd Wisdom and Charisma scores.
Maybe even under 10 in Charisma, Wisdom, or both? Like, Wis 9, Cha 9. Becoming a Modronoid might not be very good for the mind of an ordinary humanoid.
Armour wise, you were proposing one point better than a Pentadrone, which'd be either +10 NA (
Dragon) or +5 NA (WotC).
The former would give it AC 21 with Dex 12, which feels a
little too high. The latter gives AC 16 which is way too low.
Hmm… I'm leaning towards Dex 14 and a +8 NA bonus for a nice round AC 20.