If you want crafters to take part at PvP, the only way is how to make Repair/Science influence on fight.
Science:
"Covers a variety of high technology skills, such as computers, biology, physics and geology."
For example low science = you're hairy ape who don't know how much will be 1+1, so I can't understand how such person can wear high grade equipment and work in team with someone. High science means knowlegde of physics that will help you to shoot/throw properly, biology to do aimed shots properly and of couse science will make you able to use covers like barrles/boxes/trees to avoid bullets. High science skill allows you to analyse the situation of fight. Also science skill will allow you to use all this high tech stuff, also repair can be used for it too. At least use it better than low science.