Google Maps Missing Navigation Options

The first tool I generally turn to when planning a route to an unfamiliar place is Google maps. But the routing options do not include some of my key preferred options.

Scenario

Travelling from Brize Norton to Trafalgar Square.  Imagine you have just gotten a weeks leave pass, and have just arrived back in Brize Norton.  The first thing you may want to consider is to head into the capital, and kick back a bit.  

My first though would be - can I use public transport for this?

Option 1 - Public transport - seems slow.

the answer is obviously yes - There are links there, but this seems like an awfully long time. If one has a car option that may be quicker.

Option 2 - Drive - but where does one leave the vehicle?

A vehicle route may be quicker, but this seems a little silly - where does one park?  Could I just have driven to the station in the first place.  Knowing a little about the area - I know that I could drive to a station with a car park, such as Didcot Parkway.

Option 3 - Part 1

Option 3 - part 2

Breaking the route down requires more area knowledge than for option 1 or 2, but is more akin to the way that I plan a journey in a place that I know well. Is it the optimal journey - probably not, I also know that other rail stations exist with large carparks.  Some charge different amounts for parking, and some take a long time to get into.  In places I know less well I suspect that there are many more options for route optimisation using a combination of travel modes. For instance there are large carparks at Houndslow west and Watford Junction. Driving then parking to switch to either public transport, or cycle are two of my preferred modes of going to places in bigger cities.  Adding cost information for public transport would also aid in finding the better route options. 

Are there a good cheap car parks in London, or our other larger cities, that are within cycling distance to the city center? 

On the surface of things Google maps gives you some great options - There are options for Driving, Public transport, cycling, and walking.  Whats missing are the mixed mode options that I tend to look for and take. Adding these mixed mode options also benefits the cities that are travelled to.  Using park and ride, or park and cycle, facilities reduces congestion and speeds up journey times for other travellers.