I was looking for an ascended class for a IG commander character, but none really fit the bill for a highly charismatic leader of troops. Does anybody have any house rules for an ascended commander, like the Lord Commander Militant. Failing that, any suggestion on how to build one?

A Gaurdsman who took the Officer path and ascended as a Storm Trooper who took the Specalist: Field Command ascended trait perhaps?

Dunno if you can cram enough non-personal combat advancements into the Stormtrooper.

However, you might try to go with Interrogator - its Skill (Any) and Talent (Any) slots can be used for customising pretty well and it has cheap Intelligence and Fellowship advancements.

i'd go with... IG base, then Chaliced Comisariat for all its worth, then go the commander route up to 8th, at 9th i'd hit either Interrogator or Storm Trooper, depends if you want a Leads from the Front type of commander or a sits in orbit commanding the troops on the ground with inspiring speaches type of leader..

Arbritrator -> Judge?