HT, thanaks for your thoughts. I do share many of your concerns.
On the positive, providing an hourly service on the Barton branch would benefit the reasonably well used flows from Goxhill and New Holland to Barton.
Providing a regurar service for Kirton Lindsey and Brigg is also clearly a positive. However, I would imagine that whilst their main transport demand is to Scunthorpe, secondly to Lincoln, which is always going to served better by omnibus services than by changing trains at Barnetbyin terms of journeys that could be offered by the railway travel to Sheffield (which is provided by this service), Meadowhall, Grimsby and Cleethorpes would all be more popular than Barton, indeed the low loadings on the 450 bus service demonstrate the lack of Barton - Brigg demand.
In terms of connections off the Barton branch, ,Habrough provides an easy level access connection. I would imagine the time saving for passengers changing for a Lincoln or Doncaster train would be in the region of 5 minutes, in reality they would almost certainly end up on the same train either way.
The benefits of the connection to Humberside Airport at Barnetby are in my opinion overstated. The passenger numbers at the Airport are low to start with. Anybody travelling from Barton by public transport would just catch the 250, similarly anybody from Brigg would catch the Wolds Villager. Sheffield has a direct rail service to Manchester and Birmingham Airports. I imagine that the number of people from the other intermediate villages travelling to Humberside Airport by any means to be negligible.
In terms of London connections at Retford, if timed right I could see people using it.
For those making long distance journeys off the branch in general, it will all boil down to personal preference. Unless actually going to Brigg, Retford etc, I can't see that there is much to choose between changing at Habrough or Barnetby, you would almost certainly be on the same trains either way.
Travelling throughout by train has the advantage of one through fare, in many cases at the same price as it would be from Barnetby and if one leg goes wrong the railway are obliged to get you to your destination.
Going by car to a railhead, for those with the option, will be quicker but has the associated fuel and now parking costs at either Barnetby or Hull, together with the risk of struggling to get a space at the former.
Using the Call Connect bus will have a cost for many and journey time will be variable. Certainly from villages such as Barrow and Thornton Curtis this must be a winning option.
Using Humberlink to Hull is probably quicker for some journeys, especially if going via York or Leeds. Certainly during the day good connections are guaranteed, it is just a shame there is no period return fare. Indeed, really this could do with having rail tickets accepted on it.
As for the suggestion of an express bus to Brigg / Barnetby, I wonder if this could be a use of the short 250 workings, which in their current form carry fresh air between Barton and the Airport. They could perhaps extend to Brigg and either them or the through Cleethorpes services could divert via Barnetby.
I suspect Hull-Barton-Brigg even without serving Barnetby would be at or very slightly over an hour each way, so couldn't be done with 2 vehicles on an hourly frequency, or if it could be done, there would be no recovery time. The 'shorts' had 42 minutes between leaving Barton Market Place en-route to the airport and returning. Barton to Brigg and back non-stop in 42 minutes, yes, but add in hopefully some stops for passengers and any waits at traffic lights in Brigg, and 42 minutes seems like being far too close for comfort.
Hull to Cleethorpes is timed at 1 hour 52 minutes and Cleethorpes to Hull at 2 hours, so no time to divert to Barnetby on all journeys without either an extra vehicle being used or a frequency cut. When Barnetby was served once a day it took advantage of peak time variations. The morning service was the vehicle from the peak time journey into Grimsby that didn't extend to Cleethorpes, and then started 'short' from Grimsby to return to Hull. This 'short working' created some slack in the timetable so the Grimsby to Hull 'short' could leave Grimsby earlier and serve Barnetby before getting back onto 'standard pattern' at Barton. The afternoon service from Hull that went via Barnetby had a longer turnaround on arrival at Cleethorpes due to the slightly over an hour gap mid-afternoon in Cleethorpes departures; this time was used to serve Barnetby. This 'slack' was reintroduced into the timetable when Barnetby was dropped from the service.
and consequetly
was the first off peak service that starts short from Grimsby, and consequently ran 10 minutes earlier
and the afternoon service took advantage of the slightly over an hour gap from Cleethorpes later afternoon
The Brigg Line Group have published an alternative proposal for a regular service from Cleethorpes to Worksop.
http://nigelfishersbriggblog.blogspot.com/2020/06/new-shuttle-trains-could-serve-brigg.html?m=0
North Lincolnshire Council have submitted a bid for goverment money to conduct a feasibility study into the NNLCRP scheme.
The North Lincs Council / North Notts and Lincolnshire Community Rail Partnership bid for funding for the feasibility study into extending the Sheffield - Gainsborough Central service through to Barton has been successful.
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/938907/restoring-your-railway-successful-bids.csv/preview