Getting quite a few suggestions to be fair lol! Another I can suggest, although it would serve 4 counties, so here it is..
Wrexham to Llandudno via Deeside, Flint, Holywell, Prestatyn, Abergele, Colwyn Bay and Llandudno Junction.
Currently,
X9 Wrexham to Connah's Quay (reduction of Mold extension)
11/11G/ 11M Flint to Prestatyn (without alternations via Gronant/ Maes Pennant)
13 Prestatyn to Llandudno (revise route into Llandudno via Llandudno Station to Trinity Square)
I would extend it to:
WREXHAM-Glyndwr-Mold-DEESIDE-Queensferry-Shotton-Connah's Quay-FLINT-Holywell-(-Dyserth-Rhuddlan-Glan Clwyd or Prestatyn-RHYL)-Abergele-Pensarn-Old Colwyn-COLWYN BAY-Llandudno Junction
then:
LLANDUDNO
or
CONWY-Penmaenmawr-Llanfairfechan-BANGOR-Menai Bridge
services alternate:
either
Llangefni-Rhosneigr-Valley-HOLYHEAD
or
Beaumaris-Benllech-Amlwch
With connecting buses between Llandudno and Llandudno Junction to compensate.
--- old post above --- --- new post below ---
How about more brand new route suggestions?
ABERYSTWYTH-Tregaron-LAMPETER-LLANDOVERY-BRECON-Merthyr Tydfil-Pontypridd-CARDIFF
Aberdovey-Borth-ABERYSTWYTH-Llangurig-Rhyader-BUILTH WELLS-BRECON-Merthyr Tydfil-Pontypridd-CARDIFF
Aberporth-CARDIGAN-Newcastle Emlyn-Llandysul-Llanybydder-Pumsaint-LLANDOVERY-Llangadog-Llandeilo-Ammanford-Pontardawe-Neath-Briton Ferry-SWANSEA
BANGOR-Bethesda
or
CAERNARFON-Llanberis
then
Capel Curig-BETWS-Y-COED-CORWEN-LLANGOLLEN-Cefn Mawr-(Acrefair)-Ruabon-WREXHAM-Wrexham Glyndwr