I drove a Honda Prelude with 4ws.. it was awesome..
I can just imagine driving this buggy through some tight trails.. it would really rock.
The goal would be to keep it as light and small as possible. maybe under a gutted X-90 body?
I am telling you, this would work, and it would work well. Trails would be it's forte... If you didn't want IRS, you could always use a sammy front axle in the rear... but I really think IRS IFS and 4WS would be awesome..