And that is what simply doesn't make sense. We were told: Elementals can't ride anything else than an OmniMech because only its computer is programmed to handle the additional weight of Elementals holding on those handholds.
And then Magnetic Clamps (on Fa Shih BA?) came. With these clamps BA can ride on any 'Mech that see. If they ask pilot of ancient "Hot Hammer" and he allows them to do so, they can ride even this old BattleMech. No handholds needed, no problems with additional weight.
So it's obvious that the weight distribution was not the problem we were told it was...
Magnetic Clamps cause a 1 MP reduction in cruising speed. p227 TW.
Likewise when swarming rather than being carried BA tends to fall off.
The point being, non omnis need to be careful when carrying mechanized BA.
Omnis have a specialist gyro that can handle the unusual weight distributions of omnipods and BA.
Now one of the concepts that needs to be understood is just how rare OmniMechs are. They simply never made that many. Natural attrition was such that it took long periods of relative peace for omnis to enter the second line ranks.
Additionally we first saw second line units in the aftermath of Tukayyid. It is reasonable to assume that before then all Clans had a percentage of omnis in second line units closer to the Coyotes. Conversely, consider Clan Ghost Bear in 3060, with a huge percentage of Star League tech having had to suffer a historic late start in omnimechs, the losses of Tukayyid, and a decade spent shutting down factories for relocation.
Next we need to consider just what second line units do. Any combat in the Homeworlds requires bidding. Given by their superior pilots front line units can bid lower than secondline units, frontline units get most of the combat. Secondline units are rarely going to be used offensively. That means no great need to transport infantry as they mostly get to wait for attackers to come to them. Finally, strategic movement on world is by DropShip. It is easy to be moved to the chosen battlefield, then great speed is not really required.