The way I would structure my clan would be thusly:
Front Line: The point of the spear, the elite of the elite. Primarily trueborn, but if a freeborn shines SO brightly that they deserve inclusion here, I wouldn't prohibit it. These Galaxies would be staffed by the best and brightest of their sibkos, and they would be my offensive forces, tapped primarily to pursue trials, conquer ground and seek glory. Members would be graduates of their first trial of position only. Totally Clantech, 100% Omni (unless a warrior opts for a standard battlemech), Primarily Mechs, Fighters and BA. Front-Line forces would prefer and expect Zellbrigen from clan opponents, and would have the option, should a foe prove honorable enough.
Second Line: Different than the term is used in Canon. These would still be offensive forces, and they would be first-pass graduates of their first Trial of Position as well, but perhaps the troops in these galaxies aren't the elite superstars that are shown in the front line forces. They would be used both offensively and defensively, and would have a mix of Omnimechs and Battlemechs, primarily clantech or star league royal designs. Mixed composition of Mechs, Tank and Fighters, with both armored and unarmored infantry. Second Line forces would be expected to adhere to zellbrigen against other clan foes, but would not be obligated to adhere to it against a dishonorable foe.
Third Line: Primarily defensive, These warriors still have the spirit and the heart of a warrior, but perhaps their luck has not been so good, or they failed their first trial of position. Or perhaps they are past their prime, but still wish to fight. These units would be assigned for permanent defense where the clan deems it necessary, often augmented by available second line forces. They would be equipped with a mix of equipment, whatever the clan has available for them, largely Star League era mechs, but also everything on down to succession wars era gear. Administratively, these warriors would be grouped into galaxies, but their deployment would not usually be all in one place. Third Line forces would not be prohibited from adhering to zellbrigen, but they would not be expected to adhere strictly. Their honor is in defending the clan, and against a superior aggressor, dueling may not be pragmatic.
Fourth line: Reserve warriors assigned to other castes where they have aptitude, but who can be called up to augment third line defenses in an emergency. Also incorporating sohlama warriors for their wisdom and experience. Small caches of Succession Wars grade mechs and vehicles would be maintained, and the fourth line would also encompass the paramillitary organizations not covered by the Watch. Tech would primarily be Succession Wars era or Primitive/Adapted combat units. Fourth liners would not be under any obligation to adhere to zellbrigen.
The Watch: intelligence arm of the clan. Recruits whomever it deems fits its necessary criteria.
This structure frees up the best and brightest of the clan to go forth and further enrich the clan through their conquests and feats. I originally thought this up in the context of a clan effort to reestablish the terran hegemony, which would increase the need for warriors across the board. It also gives "failed" warriors a chance to redeem their honor, and prevents the clan from wasting the training that they have been given. the third and fourth line warriors may not be the fearsome Ubermensch legions that the clans are known for, but imagine how much happier a sibko washout could be, knowing that they may still get to serve the clan as a warrior. No equipment, from humble industrial mech mods, and primitives, to the mighty cutting edge Omnimechs would go wasted.
The lesser equipment in the hands of the Third and Fourth line units would be the result of conquest and hand-me-downs. Potentially importing as well, or hand-assembly. I'm not about to suggest that they go and establish production lines for inferior mechs, but what they have available, they should use. Conquest, such as re-establishing the hegemony, would likely produce quite a bit of salvage. And really, if they were building new equipment, they could replenish the first and second line units first, things could be passed down from 1 and 2, down to 3 and 4.
this is really a setup for a "clans at full-tilt war footing" concept though. Producing as much as they can, and brian cacheing what they can't use immediately. No potential warrior goes wasted. I also envision what the concept of Sohlama would entail. You get old enough, and you've either proven your worth and gained your bloodname, or you've managed to neither die nor distinguish yourself, and you either step down to 3rd or 4th line (if you arent there already), take on a sibko training role, or you retire from warrior life and serve the clan by interfacing with the civilian castes, or taking up a lower caste job when you can no longer fight.