The simplest approach is to have DATABASE_SERVER
be defined as database
(or something equally meaningful) and put an entry in your hosts file. On your local machine this can point to the remote address, on the server this will point to 127.0.0.1.
define('DATABASE_SERVER', database);
On windows your sites file is:
c:\windows\system32\drivers\etc\hosts
with:
database <remote_ip>
Linux:
/etc/hosts
with:
database 127.0.0.1
Side note: is your remote DB a production DB? If so you shouldn't really be using the remote DB for development work, unless you're using a separate dev DB - even then I wouldn't run the risk of rogue dev queries eating up the remote DB resources.
Update: Doh, missed you're limited to FTP access.