I am not saying Manston should have lots of flights.
But to say that thanet has one road in is no quite true can can use the a2 or m20 or come up the coast route.
I can only talk about my own trips.
In the last year I been on 8 flights 4 from Stanstead 3 by car and one by train all with out any problems, one did take me a while to get home, by train was ok but I the train fare was about £37 each way and a taxi from VIC to LPOOL ST was about £12 each way and about 3 hours + and you have to give you self a hour or so for check in.
The 2 flights from Gatwick. (I give myself 4 hours by road). One I was ok, but did get into a mess, with long term parking once, (transfers one per hour from park to Airport )very stress full.
I used to drive two to three times a week round the M25 to work in Swindon the road has just to much traffic, Its just full, perhaps charging you use it may help.
I have used London City which I found very good I used a taxi up and back.
What is the point of building more runways at these Airport when the transport links are no good.
What would be good for Kent is Rail links to Gatwick, Heathrow even Stanstead.
Say Ramsgate to Gatwick via canterbury tonbridge, a Tunbridge Well Gatwick used to run.
For me Manston is in the right place, I live near it.
And flights to Spain and Ireland would save me hours, and I would pay a little more for a no hassle trip.
And I am sure it would for a large area of the south east.
We will have have to wait and see.