i would NAT both sides to the same subnet, ie:
sideA - 192.168.10.10 >>> 172.16.1.10/16
sideB - 192.168.10.10 >>> 172.16.2.10/16
and/or, you can use a NAT pool for non-static hosts.
this also eliminates the extra routing hop to get from 192.168.100.0/24 to 192.168.200.0/24.