The problem with the load bearing equipment is it counts as armor for the stacking armor rules and thus combining it with real armor makes Infantry automatically Encumbered.
Still though I do consider it likely anyone intentionally building an Infantry character will already have it in mind to have a high Strength so I'm still not sold on the idea of actually enforcing a minimum Strength but the implications AToW converted to TW/TM seems to make it does suggest 6 is the minimum even accounting for load bearing equipment. Otherwise some of the heavier Support Weapons even with their weight divided up evenly amongst the crew would automatically encumber them with anything less despite not having the Encumbering trait. Part of my resistance is also the idea that according to AToW it takes a Complex Action to Pack/Unpack a Support Weapon. This would mean any support weapon should be considered Encumbering anyway by TW/TM.
All things considered though it probably would be easier to House Rule that Load Bearing Gear is designed with the idea of being layered with Armor and thus not Encumbering in that way and Pack/Unpack is a one time a turn only Incidental Action and not bash players over the head with something that I consider likely to happen anyway without having to formalize it.
Sorry for necroing this part, but I recently read through ATOW and noticed this issue.
Two other solutions. One, you can have armor incorporate LBE as part of the design, so the cost and mass are extra for a vest, jacket, or suit that employs this option. You lose the (minimal) armor value of a stand alone LBE vest in the deal.
Alternative, doesn't it seem strange that say an Inner Sphere neurohelmet will equal stagger a forty kilo weakling and an Elemental if they both pick it up? Maybe an alternate rule for encumbering equipment where due to bulk, bad ergonomics, or in the case of clothing the restrictive nature, the item's weight is multiplied by some factor when calculating encumbrance?
Something like this:
Ecumbering gear. Multiply the mass by 3-STR modifier, that is the mass for calculating encumbrance. So a character with STR 2 will barely be able to pick up a 6kg neurohelmet, while a character with STR 7 will be much less inconvenienced with it.
In terms of armor, the inner most piece is the 'base layer' and taken at standard weight, unless it is itself encumbering. Up to two more layers may be worn over it, each having an encumbering multiplier used on it's effective weight. Yes, that means if you have an encumbering over-layer the multiplier is effectively squared.