Talking of Birmingham - it's a city without the kind of cross-city services that we have in Sheffield.
Are there any cross-city routes that you think would be viable? Or does the road network in the centre (and the pedestrianisation of New Street etc) encourage services that dip a toe into the city centre but don't cross it? For example, Nottingham's pedestrianisation and ring road seem to suit the kind of network that NCT have, where buses don't run cross-city.
Birmingham also has a central train station (a few!) and cross-city trains to the Queen Elizabeth Hospital/ University area, so that's one obvious idea for a cross-city bus rendered unnecessary. Any missing links in the NatEx network though?
There did used to be cross city buses (5/6/7* - Edgbaston/ Bearwood area to Perry Common, 15/16/17 - Whittington Oval to Hampstead, 90/91/92 - Stratford Road area, Hall Green boundary and Robin Hood probably, to somewhere in the north of the city) that I semi remember but these were broken up. When I first lived in Birmingham, these routes had conductors. Later on, when Timesaver (limited stop) buses were introduced, there was a Coventry - Airport - City - Halesowen route, possibly 900 but the west of the city leg didn't appear to be too successful and was dropped, may have been the 900.
What I think did for these routes was when the Midland Red routes were taken over. For instance, Birmingham covered the Stratford Road to the city boundary but the Midland Red routes went on to Shirley and beyond (probably Solihull). After the transport executive took over the Midland Red routes in the conurbation, they merged routes so those living beyond the Birmingham boundary had more frequent buses and lower fares. Similarly, I think the Whittington Oval route was merged with a route to Kingshurst or Chelmsley Wood; Hagley Road (5/6/7) was already covered by former Midland Red routes to Stourbridge, Dudley, Wolverhampton, and others. If they had remained as through routes, they would have been very long, running in urban traffic. All of this happened before New Street was pedestrianised. Certainly, the road network in the centre has something to do with it but, at one time, there was the free Centrebus that took you round the city centre meaning you could get from any one stop to another.
Rail - the cross city line was (is?) very busy - serves Five Ways - and the line through Snow Hill from Stourbridge to Shirley or Solihull is also really a cross city line. The Travelcard system also encouraged rail travel.
One possible destination might have been the airport, but there are already links from the city centre as well as the north and south - and it is some way from the city. All in all, I don't think there would be enough take up otherwise one of the smaller operators would have taken it up.
* - there were slight variations. All buses to Perry Common (I think it went that far) were numbered 7, in the other direction buses either terminated at Sandon Road or Portland Road (one was the 5 and the other the 6). Both served Five Ways and Broad Street, where there were (are?) lots of offices. The other routes were similar. Some of this is hazy as I scrape my memory banks.
using Plaxton Elite coaches, I would have two alternating services connecting North Wales to Liverpool and Manchester! X53 and X55, both of which would run Bangor - Llanfairfechan(X53)/Penmaenmawr(X55) - Llandudno Junction - Colwyn Bay - St Asaph - Chester making maximum use of the A55 dual carriageway, with the X53 continuing almost nonstop to Liverpool ONE and the X55 nonstop to Manchester Airport then Shudehill! Each service would be hourly, making Bangor - St Asaph - Chester every 30 minutes! If this combines with the cX3 (operated by B8RLE Panther) to Wrexham, this would make Bangor to St Asaph every 20 minutes! And who says I have to use 15 coaches? I'd say about 50 (15x B9R, 15x B8RLE, 20x B11RT) would do for all these routes!
In that case, I'll just stick to the X53 and X55 idea providing better links between North Wales and Liverpool/Manchester, since that alone could be done with about 15 coaches, as well as provide more convenience for the many North Walians travelling to/from Liverpool and Manchester. It would be much cheaper to use refurbished 2nd hand coaches as opposed to brand new ones, so I would probably have a fleet of Plaxton Paragons and/or Van Hool T9s fully modernised with new livery, leather seats, free WiFi and USB charging. If the routes become successful, I would upgrade to Plaxton Elites or Panther LEs.