I was studying the above ship on a printout yesterday. I still really like it after all these years. It looks more rudimentary than the TOS era and yet it still seems to fit in evolutionary wise. Regarding modifications I'm thinking in terms of detailing because I still like the overall concept and proportions. I think it retains good visual balance.
I once thought of writing a story set in the 22nd century and featuring the U.E.S. Swiftsure
and tying it in loosely to the TOS era. The framing sequence could have been one of the TOS characters reading about the event historically or as a dramatized piece of fiction. The gimmick has been used before in Trek fiction in both John M. Ford's "The Final Reflection"
and Margaret Wander Bonanno's "Strangers From The Sky."