I'm now thinking that I'll use 8" poured concrete outer walls and 2x4 stud inner walls (filled with unfaced batts) with 1 1/2" EPS between the basement walls (13 1/2" thick basement walls).  The outer basement wall is under a 2x4 wall that supports the roof with NO connection to he floor  above the basement.  The main floor is supported by the inner (wood) basement wall, this floor also supports inner stud walls of the main floor (11 1/2" main floor wall cavity filled with dense pack cellulose)   With NO structural connection from the outer basement wall to the floor I'll need to treat all the exterior basement walls as " retaining" walls and design for the FULL soil pressure of back fill unlike conventional basements which depend on the floor for structural support.  I'll need to add some exterior "counterforts" to support the longer walls and probably get an engineer's approval to satisfy the local authorities.  Has anyone done anything similar?  Other than windows and door openings I should have almost no thermal bridges.  The roof trusses being the only other connection between inner an outer walls above the basement slab.  Your comments please.