No need, working on it, almost there…
http://forum.mikrotik.com/t/wireguard-and-placing-a-client-on-the-lan-segment-of-my-network/165017/1
That was effort #3 ( vxlan over wireguard )
effort #2 is through DHCP options
effort #1 is via WG and EOIP ( not yet done as have to deal with where internet comes from on spanned subnets)
All three were to see how one could connect a unifi controller on one router to two APs at another location. Exercise in possibilities and learning new things.