The easiest way to cheat a 'tiger' transformation is to use Lion-Os for everything but the mane and tail (tail should be a standard feline tail obtained through Catnip, Nepeta, or starting as a kaithrit) and to get Pickmentation stripes (skin accents don't show up outside the appearance screen afaict, so if that bugs you, you might be better off save editing your fur color to '[desired base color] and [desired accent color]', ex. 'orange and black').
Then you can use the language modifier system in the settings to change all instances of 'lion' to 'tiger' and 'leonine' to a similar descriptor like 'feline', 'tigrine', 'pantherine' or 'big cat'.
Note that this will mess with any words that contain the specified string of letters ('stallion' would become 'staltiger' for example, unless you add further modifiers for commonly-used words). But in the event you end up not being able to write a TF, this should serve the same basic purpose.