Portion working is only a problem because ATW haven't got half a clue as to how to do it properly, and either (a) don't know how to program the PIS to show it properly, or (b) bought a cheap and nasty PIS that can't show it properly. When it's done properly, e.g. the south WCML, or even more so Southern, it is just fine.
I can't see any way to avoid it other than making the Coast a connection, which won't be popular. Though I wouldn't mind *too* much a proper quality connection, but that would need to avoid traipsing over the bridge at Mach, or building a proper staffed, heated indoor interchange facility at Dyfi.
(Speaking of which, has anyone noticed that the 4 minute "non connection" from the last Shrewsbury-Aber to the Coast seems to have been added to the planners as an actual connection now even though it is only 4 minutes?)