I'm super high on Mobley and Okoro. Those are the only two cards I'd keep real tight to my vest in any deal.
I agree that Garland, paired with the '22 pick and say, Rubio's contract could be a pretty strong trade chip, but I wouldn't trade it for just any SF and I don't know that you have a viable option to trade him for.. plus your PG spot would be absolutely wiped out with that move which would negatively effect Mobley and Okoro's development as the ball wouldn't move at all.
Simmons/Milton for Garland/Love/'22 pick works on paper, but probably need a 3rd team and a ton of faith in Ben Simmons turning things around offensively. (though a Sexton/Okoro/Simmons/Mobley/Allen line up would win some regular season games and be a pretty good fastbreak group.)