Brogdon's one of my preferred targets to be the PG of this team and one of the few young players I'd want this team to acquire at this point. I'd replace Smart with Fournier and would seriously consider replacing Romeo for a future 1st and/or TimeLord with 2 future 1sts.
What Smart detractors don't understand about him is that Marcus aside from being elite defensively and the versatility to guard 1-4 well, he is the leader of the team, tone setter, and is reliable to not shrink in the moment regardless of it being the regular season or playoffs, 1st quarter or 4th quarter/overtime, up 20 or down 20. People faun over the Joe Harris and the other nice Regular Season stat players that become borderline unplayable in most playoff games especially on the road and in crunch time; and underestimate the players like Smart that come up big in those same moments.
The Celtics brass understands that about Smart, which is why Stevens and Udoka have mentioned him as part of the core of the team. Rick Carlisle's going to get a shot with this roster unless he deems a player isn't a good fit for his system.