SQL Server AAGs/Possible Endpoint contention/Synchronous replication to WAN Secondary
Few things that I learned from having a similar setup with my old company. We had 53 AOAGs with many DBs in each AG.


TCP Endpoint will not be a contention. (remember that you can have only one endpoint per server instance).Even with our setup having MPLS network (NY and LD) and a dedicated VPN between (NY and HK), we ran the above setup and we were fine.
with such amount of DBs, your availability group DMV queries might be slow. So make sure you use temp tables.
Since you are running SQL Server 2016, Always On Availability Groups are Turbocharged along with better AlwaysOn Parallel Compression / Improved Algorithms
Make sure you offload read work by utilizing Round-robin load balancing in readable secondaries.
Make sure you are on latest 2016 SP2 service pack.


As always, do some benchmark and testing and have a baseline to compare. This will give you confidence in presenting to management that the consolidation project indeed helped !