Seems like a very good idea, Brigg is a good sized place and deserves a decent train service, and after the withdrawl of the bus it seems like a perfect time for the service to reinvent itself. The fact that this also coincides with improvement works on the line seems to make it a no-brainer for me. The service would also provide good direct services from Grimsby through to Gainsborough and Retford, for another option to change onto the ECML.
Yes, I'm sure there'd be a fair amount of demand from both Kirton and Brigg - the 909 bus from the latter always seemed quite well used. Central station's a lot more convenient for the centre of Gainsborough too.
Call me a bit of a dreamer, but I think it'd work reasonably well if the Lincoln - Sheffield services were diverted via Finningley (calling there, of course!) and Doncaster (providing one of the Doncaster - Sheffield stoppers each hour, and also providing a direct link to Meadowhall without the bother of 'combining' services). The stations between Retford and Sheffield could then be served by an hourly Sheffield - Gainsborough Central service (with Central station rebuilt as part of the large shopping development ongoing pretty much next door)...maybe with the odd few continuing to Cleethorpes. Might work anyway!
I dont think any Lincoln-Sheffield passengers would be too keen on going via Doncaster!!!
My may concern about the plans for daily trains is the times - if they run at the same time as Saturday services then I doubt running them would be a good use of resources. Perhaps weekday passenger trains need to be a longer term ambition. Heres what I think should be more immediate things to be done
1. Add a 4th Saturday passenger train and try and extend them through to Meadowhall (maybe link in with an improved Sheffield-York service?) - dont forget on Saturday there should be spare trains sitting around that is used during the week at peak times
2. Increase the amount of Saturday freight - I think theres ony about 2 freight trains on a Saurday - This number should be increased as it wouldnt require any more signalling staff or the route to be open any longer hours than at present
3. Start weekday freight trains and make a serious difference to the number of trains going through Scunthorpe and over Lincoln high street crossing
Then may be look a usefully timed weekday pasnger service - but if there is to be any peak time service this will require funding for additional trains, and a service without peak time services (e.g. first train from Sheffield at 9am, train has to be back in Sheffield by 5pm) probably wouldnt attract enough passengers to make running it worthwhile