I setup a layer 2 bridge in my homelab using Zerotier to my datacenter. I set it up with an Asus 4 port router with DD-WRT on it. I put it together to create a use case for a client of mine. The idea is to layer 2 bridge all remote sites and default route the internet out of the datacenter. This way we only pay for the fancy firewall UTM features with layer 7 filtering in the data-center and no longer at the remote offices. Its almost been 8 months and its still working solid.
https://zerotier.atlassian.net/wiki/spaces/SD/pages/7438339/Layer+2+Bridging+with+LEDE+OpenWRT