You can put ballistic weave into many of the other clothes, including under armors, which will then give you their ability boni and 110 ballistic resistances. Why is that? Because Bethesda said so, that's why. Get to the quest that allows you to upgrade to ballistic weave, not going to spoil where it is and then you'll be confused that you can't put the ballistic weave in the vault suit. You will eventually be able to upgrade the vault suit with the "shielded" lining, which gives like 25 armor? I dunno. Seriously, i think Bethesda either screwed something up here or they wanted to include something that makes cheating obsolete. Once you can upgrade the ballistic weave pretty much every under armor is better than the vault suit.