My idea for HS2 to serve Heathrow: make Euston a through station (as far as HS2 is concerned, the WCML platforms would still be dead-ends) with tunnels and running on a deck above the M4 to Heathrow, where there would be bay platforms and through lines on to Reading. I'd also put a triangle north of Euston, linking HS1 to HS2 and to the line through Euston to Heathrow. That would give extra capacity for the GWML between Reading and London and allow regional Eurostar services from Bristol a slightly less congested route from Reading to HS1.
HSCymru. A high speed link from Cardiff to Bangor via Swansea and Aberystwyth.
It would probably need a lot of bridges / tunnels and it's existance might be suited to Welsh business / political leaders, but at least it would free up resources used on the current long distance services from North to South Wales to be put to better use. Also the WAG wouldn't need to bother with the slow long distance bus services anymore, freeing up resources on local bus routes.
Rolling stock should be a bespoke unit featuring some sort of dragon styling on the exterior (installing a smoke machine at either end would give a good effect).
It's effect would be to foster better relations between all Welsh people.
I wouldn't go from Cardiff to Bangor via Aberystwyth, there's too many reversals (2, one at Aberystwyth and another at Machynlleth). I would however build what would in many places be a brand new line with many tunnels (to allow it to be at least 75mph, which the original alignment would struggle to provide) from Carmarthen to Lampeter, which when combined with the much straighter original line (ok, I'm not supposed to talk about re-openings, sorry, but it has some long straights that should allow 90mph) from Lampeter on to Aberystwyth would make for very fast journeys. Since this is a fantasy thread, I'll ingore the time it would take to build the thing (and availablity of sufficent units) and say I'd use 158s, every hour from Portsmouth to Carmarthen via the Swansea District Line, stopping between Cardiff and Carmarthen only at Bridgend and Llanelli (maybe Port Talbot too if linespeeds can be boosted a lot) extending in alternate hours to Fishguard and Aberystwyth. In the other hour a 150 would use the new line, originating at Swansea and diverging to Aberaeron.
As for Cardiff to Bangor, here's something that's more of a new idea. Build a brand new, 100mph, 3rd-rail electrified (OHLE would probably be on the rest of the Valleys, if it's cheaper, but so as not to spoil the mountainus landscape 3rd rail it'd be through the mountains), direct line from Merthyr to Brecon (I mean direct, not the old slow winding route, you might need to fit rack and pinion equipment to the 377s I'd use on this part of the service to get them over the mountains) and do somthing to allow 3 fast services each way per-day calling at only Pontypridd, Merthyr and Brecon to get through without impacting on the stopping services.
I doubt it would be very ecconomic to electrify further, so to carry on the journey over the reinstated, upgraded to 90mph, route (I've some completly new alignments for bits of it) from Brecon to Builth, Llanidloes, bits of the Cambrian line (with speed upgrades) and a new line from Porthmadog to connect with the line south from Bangor and Caernarfon you would change to a 158 at Brecon. Both the 377 and 158 services from Brecon would be hourly, the 158s alternating their northern destonation between Wrexham/Manchester/Liverpool (via Oswestry) and Bangor/Holyhead.
The 3 fast services each way would be 57s plus mark 3s in WAG express livery (the plain locos rather than the branded ones, but perhaps with a Welsh dragon in white painted on them) running right through from Cardiff to Holyhead (replacing the current express service between the two via England, I'd have similar trains going that way though, but terminating at Llandudno). Ok, my route still has a reversal between Cardiff and Bangor (at Newtown) unless you feel like missing out a major intermediate town, so the 57 would need TDM and there'd have to be a simarlly liveried DVT on the other end.
I wouldn't ditch the long-distance bus services, and I'd have a lot more routes, as they are very helpful in reducing the number of changes necessary to get about by public transport. The Optare Tempos are also a massive improvment over the quality of most of the other buses. However the new lines would relegate them to the secondary status they should take, and I'd throw out the idea for coaches (unless they are actually nice and comfortable to travel on and suitable for frequent stops in the middle of nowhere, unlike any coach I've ever traveled on) and clone YJ55BKE or YJ55BKF (the Optare Tempos used on one of the TrawsCambria services, which thanks to extra legroom are so much nicer than the others) to operate the network.
