Will it be practical... Not overly.
Will it be blisteringly fast and able to solve many of the problems facing mankind today... Nope
Will it be challenging... Yes
Will it just be useful... As an academic exercise in how not to design your own CPU instruction set, almost certainly.
On the plus side you can build it yourself as a test-bed for experimentation and who knows, it may be a stepping stone for "you" helping to solve many of the problems facing mankind. So, if in the future it does help you in this endeavour, I'd like a mention please :)
In the mean time, you can follow my progress, or lack of here.