Derby station is hardly in the middle of Derby anyway
Toton seems a very sensible decision to me - close enough to Derby, Nottingham, Mansfield, Loughborough and East Midlands Airport for anyone to consider driving. The only downside is it is north of Trent Junction, so not so easy to make links with trains coming north from Leicester towards Nottingham and Derby.
By the time the line is built, Nottingham and Derby will probably be one vast sprawling conurbation anyway.