I think Conley for Horford is a lot more realistic from Philly’s perspective. Plus, I think Harris is a poor defender.
I would consider Conley for Horford and Richardson. I really like Richardson and think he would be amazing next to Mitchell. Horford and Gobert would have a lot of same strengths and challenges as Favors and Gobert, but Horford has better playmaking and range. The team should be much better defensively and hopefully not hinder the offense.
Horford is definitely overpaid, but he has fewer years and dollars on his deal and because his last year isn’t fully guaranteed he could be a good future trade piece going into that last year of the contract.