What is the danger of using interrupt pre-emption in ARM
In general, interrupt preemption may cause deadlocking problems: if an interruption waits on a resource that is locked/in use by another lower priority interruption, you program may stall.

Also, a higher priority interruption may well interrupt a task which should not be interrupted if not properly protected (critical sections).  When not using interrupt preemption, disabling interrupts on a given level disables all interruptions.  When nesting, you may have higher priority interruptions breaking code from lower priority interruptions/code in unexpected ways.

Frankly, unless you really need to prioritize a process over another, it is useless to mess with that.  Since you look like your are only chaining interdependent processes, i would only call this asking for trouble.