What is the feasibility of an elevated home extension - versus adding a floor inside a 16-foot high basement?
Based on your drawing, and the picture from your previous question, your basement/crawl space does not appear to be a good candidate to turn it into living space.

The only thing that basement is really good for is storage. It would not make a good living space because there appears to be a moisture problem there. Any kind of construction material placed down there would get damp and moldy. It also doesn't appear to have many windows, so those would need to be added.

An addition would be a good way to add some additional space. However, that would be very expensive. That is not a DIY job, and it will require you to hire an engineer/architect, general contractor, carpenters, plumbers, roofers, etc. You would also need to have accurate architectural plans drawn up and submitted to the local building inspector just so you can get a building permit. If you are building close to the edge of your property, you may also need to have a survey done to make sure it is set back from the property line far enough.

Unfortunately, it is not like the old days where a home owner can just slap up an addition by themselves. There are a lot of rules and regulations that need to be followed. If you do build without permission, the town or city can force you to demolish the entire addition. Another thing to consider is that you would also have an increased tax liability. When the construction is complete, the tax adjuster will reappraise your home, and the amount of taxes could jump significantly depending on the extent of the renovation.

So the bottom line is how much you are willing to spend to make your home larger. It may be more feasible to make better usage of your existing space, before making the leap.