Have an 1812 with 4 interfaces. 1-Internet, 2-VPN (attached to 1, no NAT, no split), 3-PUBLIC(NAT to 1), 4-PRIVATE (no NAT). Each with its own IP addressing and all works great with one exception. What headaches will I if I set the VPN to use same addressing as used in PUBLIC interface. VPN users just need occasional access to network equipment in 3-PUBLIC to maintain and monitor it. Nothing more.
I have this problem too.