Advanced Training (HoH): OCC, MOS, TLA

[Curbludgeon]

Based on the Melee Specialist thread I began looking to see which OCCs work well with taking Advanced Training. Depending on how much overlap one is trying to either incorporate or avoid most eligible classes can take one course at around the same opportunity cost. To take two costs between 8-10 OCC Related/Secondary skills for an existing character, and all OCC Related and Secondary skills for a starting character, with the latter having an option to exchange 4 more skills later for a third AT. Two of the OCCs in HoH start with one AT preselected and two choices, with a third at level 5, for a total of four ATs.

I have a couple of questions:

What are some OCCs that can best exploit this system? If taking AT as an existing character that would mean OCCs with a lot of skills gained during level advancement, while if taking AT as a starting character that means OCCs with extremely few skills gained during level advancement.

The CS Demon Slayer OCC (HoH pp105-106) has no OCC Related or Secondary Skills by default, and automatically selects two ATs, with a third selectable at or after level 5. Does that third AT require losing OCC skills, as with other starting characters, or is that cost already factored into the Demon Slayer OCC? While I'm pretty sure it's the former answer, especially when compared with the similarly-situated Combat Courier OCC, I think that's going to lead to a lot of Demon Slayers dropping things like Mathematics:Basic.

The AT description on pg 81 states that skills duplicated across ATs and other skills not only stack their bonuses, but those about to be duplicated expressly cannot be those traded away in order to take a new AT. What, if anything, does that mean when the AT grants Weapon Proficiencies?

What are some fun combos? While the Manhunters book might change things, a lot of the Psychic OCCs can do well with picking 2 ATs starting at 3rd level, which gives some nice options to Dog Boys and Psi-Stalkers. A Vagabond can take ATs in Rescue and Salvage Expert and carve out a pretty decent emergency responder niche.

[Blackwater Sniper]

Which book is this in?

My books have been gathering dust for a while.

[Curbludgeon]

Advanced Training is in the Heroes of Humanity Sourcebook. It's relatively new, from 2016.