I think there's two separate notions which are relevant to this
- Improving the reliability of the existing service
- Allowing extra services to run on top of today's service
The challenge is that the two of them would both require new infrastructure, but they are in conflict. To make a business case for new infrastructure it is normally required that there be some sort of new service - improving reliability in itself is not transformational. However, any extra services added would then dilute the extent to which the service could be made more reliable. The best case scenario is that there is some sort of infrastructure improvement possible which would deliver more new paths than would be required to justify its cost, allowing a little bit of extra headroom at the same time as enabling new services. Even then though, unless there's a much bigger and more difficult bottleneck after it, it's still quite probable that the excess capacity would end up being used for more services again.
What is the future of the north west Glasgow electrics service? The 2043 Route Study is a good place to start since it shows what the professional railwaypeople of Scotland think will be needed in a few decades. Quite notably they do not include extra paths on these routes, as the existing service pattern is actually not a problem. Therefore, it's going to be particularly hard to justify spending hundreds of millions on a capacity improvement when there's no fundamental need for it. There are a lot of capacity constraints across the Low Level networks which are getting fairly balanced now. More trains through Partick would be a nice thing to have but where do they go east of Bellgrove, or Rutherglen? The route out to Airdrie is constrained by the need to serve many suburban stops while also allowing a competitive end-to-end journey time to Edinburgh via Bathgate.
The sort of upgrade they're proposing for Hyndland would be fairly doable, since most of the land is under railway ownership. Realistically they could get most of the way there by going slightly further with the plans they had for a third platform at Hyndland. By fiddling with Hyndland East junction and the entry into the existing loop/proposed third platform line you could enable another parallel movement. There's going to be a conflicting movement somewhere and I would very much imagine that allowing trains from both Anniesland and Jordanhill to enter the platforms simultaneously is more important than the other way around. In the worst case scenario any wait to go westwards backs up eastwards through Partick onto the grade-separated Finneston junction through the existing bottleneck.
Fixing the single lead junction at Westerton seems like it's going to happen, even if just to give a bit more clearance for trains to not block at Hyndland. The benefit of redoubling Balloch or Helensburgh will be much more limited by their distance from the core and the fact that recovery turnback points are available at Dalmuir and Dumbarton Central. Fixing Bellgrove is probably also less important given that it only directly affects the Queen Street service and is limited to 2tph.
I've said this many times before but I would expect any real interest in spending hundreds of millions of pounds into expanding the transport network north-west of Glasgow to be spent on metro projects. The best way to improve Hyndland-Partick is to bypass it entirely on a street-running tram and then dedicate the existing heavy rail network to serving exurban passengers.