I want NO part of having 2 mid thirties max contracts on my roster in 2-3 years though.
Millsap on a 3-year max deal might be something I could stomach. At least both him and Horford would have expiring contracts.
But I'd prefer a number of other options for a variety of reasons.
If we could sign him for a 3 (2+1 player option) year max deal I would be very pleased. He is an excellent all round player. Not a world beater, but a guy I would go to war with. After Hayward, he might be the 2nd best free agent on our board. We would still be one scoring wing short (PG, Jimmy, or JB might fill that need in a year or 2). For some time, I disliked the idea of Atlanta's bigs redo in Boston, but with much better perimeter rotation and a solid true rim-protecting 5 (Hopefully Žižić in a year or 2, or a ring chasing vet as an immediate help) we are NOT Atlanta 2.0. We would we a very versatile team with a great veteran/youth combination.
However, at his age, I am not that convinced that Milsap will be looking for a deal with less than 4 guaranteed years. He might bet on himself and do that 2+1 to re-up in 2 years.
There are many different paths for us to get better, this is one of them.