Fortigate Network Setup/Design Question

Hello, I have a network with a variety of switches that feed back to a Ubiquiti Agg Switch. From the Aggregation switch, I'd like to run an LACP trunk - 4 x 1GB connection to my 200E. I'd like to use the fortigate (rather than a true layer 3 switch) for routing and to improve security between network segments and subnets. I'd then create virtual interfaces on the fortigate under the LACP connection for the 10 vlans that I use and have identified in my unifi controller. So my 200E would essentially have one WAN connection, one management connection and 4 cables in a LACP trunk to handle vlan traffic from the Aggregation switch. Am I thinking about this correctly and is this a good way to design this?