At the risk of taking this conversation round in a big loop, I would still maintain that they can play a role in the classroom but that as with any position the responsibilities need to be clearly laid out for them.

Is it a difficult job to carryout some of the remedial tasks that i've described in previous posts form the basis of a TAs role? No, it isn't.

Can a TA take some of the strain off a teacher and allow them to focus on their primary role of teaching a class? Yes, they can

Can you find Chinese Uni students who are capable of carrying out these tasks? Yes, you can

Is there an inherit danger (as I initially posted and which Turnoi has further discussed) that these TAs are feeding info back to non-academic management who may seek to undermine your position for whatever reason? Yes, there is that danager

Is having a TA for the majority of classes essential? No, it isn't

Basically my stance would be if the TA can perform their role then all is well and i believe they can have a positive impact on a learning environment. If they can't or worse still if they are actually undermining the teacher and damaging the learning environment then i would have no qualms about kicking them out of my class.