Looks potentially useful!
Indeed ... I've been following the Great West Way quite closely / know what "it is". Some of the choices of what's included and what's not look a bit odd to me - but then I'm sure there are reasons and it's very easy to criticise when I don't have background to the "whys"s and "wherefores".
The "Great West Way" is designed to help (or is funded by a government fund for) independent overseas travellers reach the wide range of places worth seeing, but away from the "Honey Pots" like Windsor Castle and Stonehenge - spread out the visitors for the general economy benefit of the corridor rather than having just a handful of places overcrowded taking the benefits without "spread"
Very interesting to note that - unlike other rover / ranger tickets that cover Paddington to Reading - the Thames branches are NOT included. No Windsor!! (No Marlow, No Henley). It does not include the train too Oxford ... though you can get (on the Eastern ticket) to Oxford by bus from Reading or Swindon, to Windsor on the GreenLine Coach from Slough. I would have thought it useful (and thinking for tourists) to have included Waterloo to Reading, and Reading to Basingstoke - certainly on the 7 day ticket. But then that latter would mean including travel on Cross Country who are not part of the scheme.
Looking further west, Devizes can be reached from Swindon and Trowbridge on the tickets. It can be reached from Bath in the evenings and Sundays only, and not from Salisbury or Pewsey (even though other services from the same operator are included on the ticket), and not from Chippenham (none of the services of the operator of that route are included. The tourist destination of Corsham can be reached on Sundays and in the evenings. Both Marlborough and Avebury are included, but the short bus hop between them is not ... all in all a very interesting choice in Wiltshire
Looking further west again, the ticket takes you to Bristol Temple Meads - but only via Bath Spa. As some services shift to running via Bristol Parkway, they're not included. And you can reach places that, surely, tourists may want to see like Weston-super-mare and Avonmouth (and Nailsea) by bus but not by train.
If excellent combined timetables and an app with a journey planner are produced and the whole thing is thoroughly marketed, it may well be a runaway success in its intended market. If the information is not joined up, clear, and available in multiple languages, I see risks. I hope a risk assessment has been done and solutions / mitigations planned.
