[Endoperez]

Strength and Encumberance are independent. Agarthans are strong, but they all look as if they are out of shape. Ulmish troops are stronger, but have normal encumberance, while Machakans have normal strength but lower encumberance.

Strength-increasing magical effects are a different story; just look at Girdle of Might (gives reinvigoration).
It would be nice to have certain magic items and perhaps even spells to lower the affected units' basic encumberance by 1. On one hand, it wouldn't be fun if any enc 4-or-less commander could get to enc 0 with a few items, but on the other hand all undead get enc 0 for free.