First of all, you got 6 switches but you named them in pairs. If these switches are not stacked, just use leaf-1 to leaf -4 and boarder leaf-1 boarder-leaf 2.Better notation. I am assuming that you are thinking of using eVPN in your topology.
you can use all topology as you suggested as a layer 2 network, do not use any VLAN IP address, and set your gateways as ASA IP addresses. This is called a centralized model, where routing is done via selected nodes or devices.
Good side: Your configuration will be super easy. you just lay your VXLAN tunnels and you are ready to go. In fact, you can do all your routing on firewalls for getting in and out of topology.
Bad side: Any traffic will go through firewalls even if you don't want it. Imagine you have two hosts on the same leaf in different VLANs. Their traffic will hop through border leaves and come back which will create additional traffic.
If you keep your anycast gateways and set your host's gateway as leaves than you can use Policy-based Routing (PBR) to redirect the traffic to firewalls. You can still choose to do your outside routes either via firewalls or via border leaves. It is better to use symmetric routing in this case.
Goodside: Since you keep your anycast addresses, host-to-host traffic will flow faster with less overlapping traffic.
Bad side: More configuration and more work.