If that is the reason did it have to be Liverpool? A through train to Preston or even Blackpool North might have been useful to provide new through journey opportunities from Sheffield. I’ve often observed that that quite a number of people get off the EMR service at Manchester Piccadilly and remain on platform 14 for the Blackpool North train.
From a South Yorkshire perspective, it'd be great if Sheffield had direct trains to Llandudno/ Holyhead/ Liverpool/ Blackpool/ Morecambe/ Lake District/ Manchester Airport etc
But, realistically, the finite number of paths through central Manchester mean that capacity would be much better if we simplified things to have half hourly services from various directions into central Manchester rather than the mess of hourly services that we had pre-Covid (for example, nine trains per hour on the Airport branch with gaps of up to seventeen minutes... a Stockport - Preston and Stockport - Liverpool service which followed each other through Castlefield within a fairly short time rather than giving a balanced service on the shared route)
So, from Sheffield, I'd be fine with a half hourly service that terminated in the main Piccadilly shed... I'd be fine with a half hourly service to Liverpool via Warrington... I'd be fine with a service through to another destination beyond Manchester too but the number of through passengers would be so small to make any pairing fairly inconsequential (in the way that it doesn't really matter whether Metrolink services from Bury go to Didsbury or Altrincham or Ashton, as long as they provide a good frequency from Bury into central Manchester)
Whilst the Warrington Central route isn't the "fast" Liverpool line (the services from Lime Street get overtaken by Chat Moss services in terms of getting into central Manchester), it's an unelectrified line that probably needs something like a four coach 158 or six coach 185 every half hour, which means it ties up pretty neatly with the "fast" Hope Valley services - the two match up pretty well.
The alternative would be generally either wasting DMUs by running them under the wires (e.g. Sheffield to Blackpool) and I'd rather that we utilised our scarce DMU fleet on the unelectrified liens where possible... or running the Sheffield services to somewhere that doesn't require the same kind of middle distance DMU (e.g. an Atherton stopper). Liverpool - Sheffield every half hour would work fine, since each side of Manchester probably deserves a fairly similar frequency/ type of train
The CLC ought to have services to 13/14 (given that it can't go to Victoria), so where else can you send them? The Airport branch is electrified, which counts against it... Buxton is a possibility (half hourly DMU service) but that's been more of a "150" route than the 158s that have tended to run faster service on the CLC
Cleethorpes is a great day out on the train (I did it last month - the station is brilliantly located in the town), but it's not about through passengers (just like Metrolink aren't designing service because of the Oldham - Eccles market). That said, they do make an effort in Cleethorpes in terms of putting on things like Armed Forces days/ Mod days, which attract a few people from outside the area.
The problem is that, if you offer people a service to Oxford Road (for the University) and the Airport then they'll say yes - everyone would prefer a service to at least one of those two if they had the chance - but we can't cope with that number of services - so we should focus more on giving places a good balanced service into central Manchester and trying to tie up the places either side based on places that deserve a similar frequency/ type of stock (e.g. unelectrified lines east of Manchester to unelectrified lines west of Manchester)
