Funnily enough I just picked up the McCabe set as well!
I don't intend to use Wastrels with him, although I know they have the "synergy" I think that 10 thunders are flooded with amazing minions that they just don't cut the mustard, and as a Brit that truly hurts me, especially as they have a trigger called "fiver says I can do it again".
After doing some number crunching with my current set I came to the conclusion that there isn't a bad set of models to go with Mccabe, he's very unique in where he does generalist upgrades that just makes people "better", so he makes a good model even better.
One of his best synergies (in my opinion) is with our Dawn Serpent. One of, if not the strongest minion in the game means that Mccabe can use Black flash with his badge of speed to give it reactivate (which only works on minions) then chuck the badge over to him, Illuminated are a watered down but also a great option if they are super low as they have Regen and a 0 action heal and are just a solid minion.
I'm planning to run him with Izamu, getting him into the the thick of the enemy and giving him the Regen+even more armour. In my mind that will make him an iron block (the 4 inch push on upgrade delivery also greatly helps him because of his stumpy legs).
Im also planning on running lone swordsman with him, thematically he's my favourite model and I love his tool kit, but unless you know your going against a heavy shooting list he can be slightly squishy. Having a reliable armour, even armour+1 in my mind will make him much more rounded.