Can someone do a sanity check for me please? Is this possible? Here's the situation.

We have an OC300 on the network for our controller. We have a TL-SG2428P in the rack in the main building with an EAP610-Outdoor running on POE from that switch. There's a big steel walled building (kind of like a metal barn) with no windows on the property. The EAP610-Outdoor (mounted on the main building) is pointed directly at the steel building with direct line of sight and only a 200 ft distance. This is in the middle of nowhere, so very little signal interference of any kind. The WiFi signal outside the main building is fantastic! The WiFi signal inside the steel building is non-existent.

I'd like to use an EAP225-Outdoor to go "wireless mesh" from the main building's EAP610-Outdoor. Then go to a small 4-port POE switch inside the steel building. Off of that POE switch, we would connect a wired EAP225 ceiling mount to give us WiFi inside the steel building. Is this possible? If so, what does the configuration look like? Do I need to set up a separate SSID with a different name for inside the steel building? Or can this all run on the same SSID so we can easily "roam" from inside the steel building to outside on the property?