We had a similar situation after acquiring two competitors. We worked with SSP https://geomotiv.com/industries/adtech/ssp/ to build a unified custom SSP handling all properties while allowing property-specific optimizations. Implementation took about 9 months. Now we have one dashboard and reporting system across everything but can still customize demand partners, floor prices, and algorithms for each property. The operational efficiency gains have been massive - one tech team instead of four, consolidated billing, unified analytics. Eliminating four vendor fee structures paid for itself faster than projected.