If it becomes a madrasa or a college of inculcation only,that could be hugely problematic .
这句话中只有两个主谓结构,已经有了一个连词“if”,为什么还硬要把“that”看成是关系代词呢.两句话之间只能有一个连词.
that could be hugely problematic .是这句话的主句.
如果将这句话这样来安排：
That could be hugely problematic,if it becomes a madrasa or a college of inculcation only.
你还会认为这是定语从句吗?
如果不是定语从句,那就无所谓“限制性”和“非限制性”了.