One of the latest designs we have been working on at IP ArchiTechs is using eBGP and an OSPF transit fabric to provide traffic engineering and load balancing. If you missed this presentation at the 2017 MikroTik User Meeting in Denver, CO, here are the slides:
WISP-Design-Using-eBGP-and-OSPF-TF-traffic-engineering-MUM-2017_KevinMyers-4-by-3