Re: Reason for Reliant's number?
If we go with the "18 represents the 18th class of ship" theory, the Reliant is only one class newer and could easily have been refitted the same as Enterprise.
Even if not refitted but built as seen, it could still be the next class of ship and not be too much newer. Starfleet probably wasn't churning out new ships like we saw around the time of FC.
Rimmer, on what period of history to live in-
“Well, It’d be the 19th century for me, one of Napoleon’s marshals.
The chance to march across Europe with the greatest general of all time and kill Belgians” - (White Hole).