This is a VERY important question as I plan to deploy this for the entire town in 10 days.
If I enable Drop In Mode on WAN1 of PEP.
I would then place my ISP routers IP, 172.16.99.254, in the WAN Default Gateway field box.
My office router 172.16.99.253 would then have a default route of 172.16.9.254 and my office is happy.
My IP on my LAN port is 192.168.130.1 and my non-office customers are on the 192.168.130.0/24 net with 192.168.130.1 as their default gateway.
172.16.99.254 provides access to other private 172.16.1.x/xx locations that devices behind 172.16.99.253/30 would need access to. I understand this should work fine.
The question I have is->
Would customers coming in the 192.168.130.1 LAN port of the PEP be balanced to access internet via WAN default router of 172.16.99.254? These customers can keep their 192.168.130 IP as at the very end of out networks where we have our Internet POP we NAT.