Veteran feats are a let-down despite how late you get them, I made a forum post about it once. If anything excess strength should reduce effective armor penalty, but that's another matter. Body Weight Training is a rather weak feat considering that it actually gets outdone by a regular feat, either the effect needs to be a lot more substantial or it should be repurposed for something else entirely that still benefits tincan builds.
The reason body weight training is so much worse than nimble is because it can potentially allow you to go under 20% armor penalty with super steel armor, if you combine it with armor sloping and specialization. You can then use it on a fist build with lightning punches to deal high damage, have high mobility, and be extremely durable. Body weight training is fine as is.
You get it at
level 25-26 minimum, at that point in the game you're killing anything no problem, being tanky on top of that because you built for it this whole time is just cherry on top.