Hi JC,
Don't worry about the static mappings, you can still use NAT 0 between the VPN endpoints. Just add to NAT 0 the same ACL as the crypto domain (LAN1 to LAN2).
The alternative is this:
All the hosts are PATed to one Public IP.
In addition a static is created for the FTP port(s).
Configuration for one end:
nat 1 (inside) LAN 1
global 1 (outside) Public-IP-1
static (inside,outside) tcp Public-IP-1 20 FTP-server-IP 20 netmask 255.255.255.255
static (inside,outside) tcp Public-IP-1 21 FTP-server-IP 21 netmask 255.255.255.255
The VPN will be done between Public-IP-1 and Public-IP-2
Please rate if this helped.
Regards,
Daniel