Can't imagine how you would use machine with DOS and over 4G RAM. I mean, if you like DOS, why you also like new hardware?
The problem is that hardware become enormously sophisticated. Even if we do not talk about security (security and DOS, huh?), modern hardware is a "black box" with multiple levels of abstractions, designed to hide complexity and give you a "tool".
So, the only hope we do have today is FPGA. And biggest obstacle is companies which more likely will make everything to populate their proprietary FPGA chips.