It doesn't sound like an actively bad idea, but what is the goal of moving to more boxes?
I have an environment a bit like that. We have a core transit per datacenter with a bunch of firewalls leading from that transit to other things. We've split the firewalls into two types: firewalls which own networks where servers live, and firewalls which own a connection to somewhere else (an Internet connection, a WAN link, etc.). The idea for us was to provide segmentation of impact. For example, if one of the Internet firewalls goes down, only some things depend on that Internet connection.
In practice, it has turned out to be a negative. The applications behind these firewalls depend on each other such that if any part goes down, they may as well all go down. We have the extra boxes to maintain without more windows for that maintenance.