1. There are stii spurious calls from the gpws ,for ex due to terrain data from the egpws...if in visual conditions the pilot can take those as advisory . There is no fault proof system yet.The pilot should have final authority with all available help from the warning system .
Don't think the automation is the answer for all our problems.There are some very interesting articles about automation induced problems.
2 . How many belly landings on commercial aircraft do you know of? Would the system justify it's cost? Also ,I can tell you the ldg gear horn it's quite loud
3. If that would be available why the need for pilots? Just to comfort the pax?
Just get in the plane ,close the door and push the button. We call those elevators..
4. There is a taxi aid system ,on Boeing it is on the moving map on the EFB.You must have in mind that on the airliners you may not be able to install the last thing on the market ,as those new gadgets must be tested very indeep before being put on the plane. Also must justify costs,as clients are looking for a good deal also. Just compare an airbus or a boeing with some of the last bussines jets on the market.