Of what relevance are Chinley and Dore to a "fast service from Sheffield to Manchester" as the OP suggested?
City to city services are useless for commuters, it costs £15 to park at Sheffield, there's no trams or buses at get people from the outskirts of town to Sheffield in time for the pre 7am trains - i.e. The ones that get people to Manchester before 8:30am - The car park at Dore is full by the 7:15am train to Manchester, there's clearly demand for more early trains - the fast peak services generally call at some combination of Chinley and Dore, we can only dream of an intercity service city to city with no stops
An additional *semifast* may be justified, I suppose. But as for Chinley, if you choose to live in the middle of nowhere and commute to a city some way away, you choose an infrequent train service. If I was going to do something for Chinley it'd be to rebuild the station with a bay and extend the New Mills terminator.
I'm guessing you've never noticed the number of people that get on and off here. Chinley services a large portion of the peak national park, it's a popular commuter belt for the Manchester university staff.
Dore is a difficult one, it may be better served additionally by bus, as really it's a city station requiring of a frequent service not required by the rest of the line.
There is a predominant flow at Dore, and that's to Manchester, not Sheffield in my experience.