Iwould be very reluctant to change anything concerning the cataphracts. Yes there might be some writings about romans who did resist cats charges ...but remember the winner, the surviving empire writes the history, not the other way round. So the written vision is very partial.
In the end, Crassus was defeated by a combo Cat/horse archer
Roman cats were shock troops
BYZ cats were shock troops and we lack info about Asian cats
Yes hoses and riders were initially armoured to counter steppe bow cavalry but they faced also foot and lacking info is not a reason to forget bthat MEG is a game and if you want a game, you must sometimes allow for the dream and the " who knows let us keep a bamlance in what is a GAME"
Think really hard before changing anything