I agree about Stroman. I think they have to re-sign him. The pitching in the system aside from Pearson looks pretty bad/unspectacular, and we have a 3+ WAR starter who wants to stay in Toronto and is embracing the rebuild as far as helping young players. He absolutely should be extended, as long as he's not asking for an insane number.
As you said, Giles can be moved for the right haul since he's a reliever, and I think a lot of our SP depth in AAA will end up in the pen and might be potential closers (SRF, Paulino, Perez). However, the return has to be right. I don't want to trade guys just to get 40 man roster depth. Either get real prospects or improve the big league team by keeping the good big leaguers.
What I might do with Sanchez is just move him to the pen and trade him next trade deadline as a RP. It might be too late for that now (plus he has a big enough ego to make a stink about not starting), but next year in his FA year just make him the set up man. He'll probably be a better trade asset even as a rental that way than he would be as a SP who can't go 2 starts without his finger nail falling off.
I'd also look to trade some 40 man roster depth, and some fringe type prospects for more MLB help on the pitching side. Arb eligible inning eaters like Tanner Roark could have helped the 2018 rotation and could have been acquired for very little.