Nope, you don't need special feature IOS. What you are trying to do is floating static route.
However, you may need to use IP GRE through ADSL to make the floating static route work.
For Example.
Remote Router network = 192.168.0.0/24
Local Router IP GRE Interface = Tunnel0
Local Router ISDN Dialer Interface = Dialer0
! local router
ip route 192.168.0.0 255.255.255.0 Tunnel0
ip route 192.168.0.0 255.255.255.0 Dialer0 200