I am in the B- to A- range. B- if we don't re-sign Fournier. A- if this trade enables us to re-sign Fournier.
I think Al Horford is a net positive over Kemba Walker for this team. It will help us re-establish a defensive identity. It will make us a bigger/longer team. It will free up more playing time for our younger guards like Payton and Romeo.
Ideally, I'd like Smart to return to the bench, unless we can trade him for good value. He is ideally a 6th man, not a starter. That is where he has provided us with the most value historically.
I would start:
Romeo
Fournier
Jaylen
Jayson
Rob
All 5 of those pass well enough that you don't need a PG in starting lineup IMO. Great length and switchable defensive players. You have two guys who can create their own shot if things break down (Jayson, Jaylen), maybe 3 (Fournier). You have 3 plus outside shooters (J's and Fournier), you have a rim protector. You have an emerging elite defensive wing (Romeo) who can handle the tougher assignments so as to free up Tatum and Brown more defensively.
Bench:
Smart
Pritchard
Nesmith
Horford
Smart will bring his great intensive defensive energy and playmaking leadership to the second unit. Pritchard and Nesmith will be good scorers off the bench; it is reasonable to expect significant growth with a full off season, summer league, and overall growth. Horford will provide additional perimeter shooting and excellent play-making. This is a really strong second unit IMO. Better than any we had this past season by a long shot.
That is a nine deep rotation that is really decent, a good mix of experience, length, scoring and defense. That is a team that could compete against the remaining teams in this year's playoffs quite well.