“ The second biggest is that BART doesn't have enough coverage to make living without a car practical in most of the area. ”
I don’t know about the land, maybe it’s a good idea. However, this really comes down to building better mass transit.
“Closer” doesn’t need to mean distance, it could also mean time. Could Oakland be turned into “Manhattan“ with better mass transit?
As you said, closer isn't a measure of only distance it is also a measure of time. If the transit system can isn't too far to walk to, runs often enough that people don't worry about when it comes, and doesn't waste time going places the rider don't want to go: people will take it. When transit is inconvenient to get to, doesn't run when/were individuals want to go, or takes too long to get there: people won't take it.
Fixing that isn't easy though. Roads/streets need to be designed for transit. Enough people need to ride that the system isn't mostly empty. It needs to go more or less direct routes to where people want to go, not take long detours to other destinations. Only the middle depends on density at all, if you fail the other two density won't give your transit systems many riders. Pass the other two and you can still get a lot of riders despite not being very dense.
You won't be running a bus every 5 minutes through the suburbs, but you can support one 30 minutes, which is the minimum frequency to be useful, and allows 1/6th the destiny to have the same riders.
There are areas of the US nearly as dense as Paris, but because the geometry is so transit hostile there will never be transit despite the density seeming to support it. Los Vagas for example has inward facing apartments that make getting to any through street from the door hard.
Yes, it will require urban planning. Personally, I’d prefer trains/subways to buses.
The future of mass transit should arrive within a decade or so as China finishes developing low-speed maglevs that travel around 100 mph. Oakland out 50 miles should become commutable.
For now, what’s the subway situation from Oakland to downtown San Francisco? Getting people to commute in that direction would be a good start. As well as getting companies to build in Oakland.
There are a couple advantages to trains/subways over buses, but for the most part they don't apply.
They can be longer: have more riders, which is only important when they come every 5 minutes. When the bus isn't coming every 5 minutes you should address overcrowding by adding more buses which makes the whole system more convenient for the riders.
They run steel on steel which is more energy efficient. While this is a factor, a bus is so much more better than cars we shouldn't count it.