Personally, I think the Westbury - London shuttles would have to be 180.
In which case the increased leasing costs (assuming any could be found) would kill the idea stone dead.
The way to increase services at minimum cost is to integrate additional services within the existing structure.
Better use of crew resources and elimination of
ECS▸ workings could mean additional services are possible with little investment.
I have already mentioned using Westbury Crews to work the first trains of the day as passenger trains from Westbury to London as opposed to ECS trains from Reading to Bedwyn. That gives you additional services for free.
An examination of the unit diagrams would show some units not used outside peak periods. These could be used to extend Bedwyn services to Westbury off peak.
There are always thing that can be done. At the moment the separate nature of West and
LTV▸ within
FGW▸ would be an obstacle but, what was the point of the merger if not to exploit the opportunity to get a quart from a pint pot?