4 Zone System for Remodel... What is the downside?

My wife and I bought a house in NC and have gutted the property down to the studs. The home was built in 1985 and we are keeping the duct work but adding a new HVAC unit since the the original system is 35 years old. The layout of the home is a straight 3 bedroom linear line with a 4th bedroom downstairs in the middle of the house. It can only be accessed from the outside as it is more of a studio apartment.

I was thinking of putting in a 4 zone system and wondering: Under what circumstances is this a bad idea?

It seems like the the most economical approach but I am not clear on when it is unadvisable.

Thoughts?

Thanks in advance.

Anthony

source https://hvac-talk.com/vbb/threads/2227038-4-Zone-System-for-Remodel-What-is-the-downside?goto=newpost