Furthering my own thoughts here...
Lets say I have the following (obviously this isn't proper syntax):
object network inside_subnet subnet 10.1.0.0/16
interface inside (10.1.0.0/16 range)
interface outside1 (number of private IP addresses)
interface outside2 (number of different private IP addresses)
Currently I'm NAT'ing into interface one as nat (inside,outside1) source static inside_subnet inside_subnet. If I add a second line nat (inside,outside2) source static inside_subnet inside_subnet after the first it's going to be ignored because it matched the first line. If I add the outside2 nat before outside1, then outside1 fails.
Lightbulbs are starting to go off. In each of those nat statements I should add the destination ranges too, something like:
nat (inside,outside1) source static inside_subnet inside_subnet destination static outside1_IP_ranges outside1_IP_ranges
nat (inside,outside2) source static inside_subnet inside_subnet destination static outside2_IP_ranges outside2_IP_ranges