Starting in 11.5.0, there is an iRule command, FTP::port, which allows you to limit passive FTP port selection to a specified range.
You may need to specify a port range with greater than just ten ports - I would recommend at least several times the number of TMMs on your system. Unless you have near-fully populated VIPRION 4800, 100 ports should be fine. You can experiment, but you should have at least the same number of ports as the number of TMMs on your system.
You may also specify a smaller number of ports and disable CMP for that virtual server, but doing so is not recommended as it can impact performance and limit capacity.