As for the values, I think Kevlar could be +1 and the other two +2.
You are virtually deleting the third option.
"Attitude" has a number of ways to reinforce clothing/armored clothing on p.160.
Like your are saying, it's for clothing and armored clothing but does the armored clothing categories still exist in SR5? I spent the last week reading Run & Gun and wrote that... Kill me...
During an Armanté meeting
Tailors : "Look we made those badass jackets"
Marketing : "They don't look so sturdy..."
Stock management : "Did you put all the reinforcement you can? Cause we still have those unicorn jackets you made 3 years ago"
Marketing : "Yes... we only managed to sell some by offering free armor hardening with them..."
Tailors : "We know that! You can't reinforce them more..."
What I mean is : Shadowrun is a dangerous world and most of the time people will get the most protection they can leaving no market share for low armored clothing
So are your sure you can still upgrade your clothing this way or weren't those mods deliberatly deleted during the armor mechanic rework?