OK, I just got the unlock on my current character.
I'm at the beginning of the main quest line quest Getting A Clue, and my character is level 27.
I completed the quests Road to Freedom, Tradecraft, Boston after Dark, Mercer Safehouse, ( I received, but did not do Conceirge at Mercer after crafting up the place for a while.), and the first DIA cache.
I also had, but did not do the first MILA quest from Tinker Tom, and I had received but did not do the second safehouse quest.
When I turned in Mercer Safehouse after getting Concierge, Drummer Boy said there was another Safehouse and I got that quest but didn't do it and talked to PAM who gave me the first DIA quest.
When I turned in the DIA quest, Drummer Boy said that Tom wanted to talk to me, so I woke him up and he said he now had Ballistic Weave Items to offer, and after buying and selling one thing each I checked at the Armor station and the Modification was available to apply to valid clothing.
So, maybe level has to do with it, maybe agreeing with Tom, but not Completing a MILA, The Concierge quest or more DIAs or Safehouses.