Hmmm... stop me if you've heard this...
How about the Create Thrall Feat from Privateer Press' Monsternomicon? It allows the creation of permanent undead similar to making magic items. There are several types of Thralls, all listed in the Monsternomicon, some of which are intelligent, and could be serve as lieutenants. The most powerful can even cast spells.
Creation cost 5xp, 5gp and 1 day per hit die, but a couple of necromantic flunkies could work on some of their own at the same time. The feat allows the wimpiest ones to be created by someone of caster level 9, but it was designed for 3.0, when Raise Dead was a 5th level arcane spell. Since it's now fourth level, I could see lowering the entire range of caster levels for each Thrall type by 2.