I like your idea, the Daedalus looks less elegant but more sturdy than the NX and the clear seperation of ship parts might (besides the easier exchange of a new engine which you already suggested *) make it cheaper to produce which is crucial in a war.
* - On the other hand,
Drexler imagined the NX warp core to be also exchangeable, but that idea did not really transpire in the series and the exterior design of the Daedalus immediately suggests an engine exchange or rather an exchange of the entire secondary hull