I have to agree with a lot of the points raised. I have to disagree with the suggestion of rebuilding the town centre as a new undercover building - This happened at WGC and the Howard Centre is just as deserted or full of phone / coffee shops and empty retail units as Stevenage town centre.
WGC is slightly different because the old town centre contains a useful mix of sizes of retail unit, plus (at least at the time the Howard Centre opened) it was possible to park on-street (for free, if I remember correctly) outside almost all the shops. The Howard Centre also suffers from the fact that the John Lewis store is the principle attraction for shoppers coming to the town from the wider hinterland and the distance between them means people shopping at John Lewis are less likely to visit the Howard Centre at the same time. Compare that to (say) Brent Cross where people might go to get something from John Lewis, but then spend time in the shopping centre as well.
Moreover, it was never that clear to a lot of people what the Howard Centre was supposed to be. Competition with the Galleria (and the associated expensive debacle for the local council) demonstrates that it was probably one shopping centre too many in the district.
However, in light of the emerging 21st century patterns for retail/leisure it is well placed as somewhere commuters pass through on the way to/from the station with opportunities to grab food (for now or later) and a coffee. That is the model Stevenage ought to be aiming for.
The problem is that people's shopping habits have changed for the 21st century, to out of town retails parks.
That's only part of it though, and as you also pointed out internet shopping is also putting pressure on the out of town sites. What is happening is more of a holistic change in people's habits and lifestyle.
The 1960's Stevenage was built at a time where most of the shops would sell specific goods, and were more likely to be used by a "wife" who typically didn't work and instead spent time going from shop to shop buying each kind of product (e.g. meat, fish, groceries, fruit and veg they required.) They did so as quickly as possible in order to get home to do the washing, cleaning and cooking.
In the 80's and early 90's people predominantly switched to weekly supermarket shopping. The old-style town centre shops were repurposed for new activities with more focus on leisure and comparison shopping. One of the main things that remained in town centres were the banks though.
We are now in the process of moving on to a new phase where people are less likely to do a weekly shop, and also use the internet and delivery services, as well as online banking. So the reasons for going into a town centre are changing (again).
One of the key reasons remaining for going into a town centre is to get to a railway station (for those town centres that have one). For many places commuting is one of the only noticeable growth activities.
Maybe this is why the additional station work for platform 5 seems more like a band-aid as a temporary measure rather than remodelling and rebuilding the whole station as part of the project.
From what I can see it is a do-minimum scheme designed only to overcome an immediate operational problem (the excessive occupation of the down slow line by Hertford trains) experienced by the railway. There is no value added for passengers - or Stevenage itself - other than to have the previously suspended rail service to Hertford reinstated.
In that context the need to do it quickly and without bells and whistles is understandable. But it still feels like a 1980's railway stop-gap solution rather than something planned with the future in mind.