I think it would be good if Exmouth Station could be re-built so it can cope with two platforms and with more facilities than present with the staff working longer at the station.
Not sure why you want two platforms for, Exmouth station is at the end of a single line section from Topsham. Therefore train comes in, train goes back out again. Second platform and signals mean one train just sits there wasting fuel / crew time for half an hour.
If you put in more loops etc all this means is that the trains will be reduced to a stagger as they pass each other just as they are at Topsham now. The journey times would increase and more units and crew would be required just to maintain the existing level of service. If your going to increase the number of stations (Newcourt for example) the ability to maintain a half hourly service would be put at risk unless you shut Polsloe Bridge which is adequately served by local buses and is going to be very expensive to upgrade for DiPtac / disabled access.
What needs to happen I suspect is the lengthening of existing trains, preferably with new units along with longer platforms and upgraded facilities at the more heavily used stations.