Re calling the MRA4 a Nimrod...........................it doesn't matter, it is just a name!
If they did change the name then what? Would you claim they were trying to hide something or complain about the waste of money in renaming all the publications, etc?
The fact that the MRA4 looks like a bit like the MR2 is a good enough reason to call it a Nimrod to me. No one seems to have an issue with the Hercules C4, C5 (C130J) or Harrier GR5, 7, 9, T10 and even the Spitfire ended up all most entirely changed with different wings, engine, canopy, etc.
The name won't affect its safety, if anything it will remind us of what has happened and help ensure our fleet strives for the highest standards of airworthiness possible.