Shagrat (or his chum Gorbag) could have made for one of the
Professor's semi-throwaway stories (no doubt uncovered
in a philological investigation into the origin of orcish) or
perhaps as part of a "Concerning Orcs" section at the end of
LOTR. Perhaps something like the bit on the Druedain in
Unfinished Tales.
Then again one can imagine a chronicler in Gondor penning
a revisionist "Grima's Tale" with a sympathetic backstory
of unrequited love, working to save Rohan from inevitable
destruction, etc.
Hmm.
+ + Shagrat. Who would have made mincemeat of
The Great Goblin if he had been able to get back to
freelance gangsterism (just like the good old days with
Gorbag).