Your forgetting the decade it took to come up with the design, layout, etc... for your Galaxy scenario. Lets not forget any amount of Red-Tape that also goes along with a new design.
I don't know if additional crews could be added to the process (depending on what you consider a 'crew'). I should take millions of man hours just to lay the basic hull components in place for that size of a ship. One other thing to consider, it probably takes less time to build a ship with older/stock components vs. a cutting edge tech design ship of the same size/SU total (Example: Miranda vs. Saber or Defiant).
Phoenix...
"I'm not saying there should be capital punishment for stupidity,
but maybe we should just remove all the safety lables and let nature take it's course"
"A Place For Everything & Nothing In It's Place"