Just to confirm. After a serious internal review, it was determined to disallow the carrying of any live cargo inside a BattleMech.
This is due to a number of reasons-
The nature of BattleMechs, with their very restricted internal space (which is often if very odd shapes), precludes space properly sized to fit living creatures.
The motive style of a BattleMech creates an uneven and unsafe ride that is hard to protect against.
Related to the previous bullet, it would require whole new rules on how to deal with damage to living cargo.
The IndustrialQuad from Klondike seems to be an exception. I'm not sure we ever got to the errata, however the intention is to adjust it so it is carrying an external cargo module (like what is seen on cargo ships today). External cargo modules can carry infantry.
There is also a fiction reference to a DA IndustrialMech that disgorges infantry from it's arm. This unit was using a skip loader attachment with the infantry hiding in it.
Thank you,
Joel BC
BattleTech