What I would do with the design
I WOULD keep the JJ-style nacelles, but thats becuase of how im making X-Ships.
In FoaS-trek there is an involved lineage of design. There was the early early early stuff - ie: things from the Starfleet Museum, those led into Kelvin-esque and NX-esque ships. Those evolved into TOS ships. Then came the first definate generation of X-ships. When starfleet made its major overhaul after TOS, it took a few contractors to design a series of X-ships. The JJ-esque-style (for me) is going to be among them (by one designer), there were also things like Schtupp's monitor (which ultimately one the contract) thus giving you the TMP ships. Among those X-sihps would be the TOS excelsior, but the design was shelved.
After TMP, a second line of X-ships came out (these will be the X-ships from SFC). among them was the Excelsior, which was done by the same designer as the TOS excelsior. This time they won the contract over the designers (of the SFC X-ships), thus giving you the TMP excelsior, and even the Ambassador.
BTW: all the "-esques" (ie: jj-esque, NX-esque, Kelvin-esque) all have my own spin - as usual :-)