I have thought about the same issues somewhat.
I believe that the reason the high end suits have not been surpassed are because of a few simple things :
In order to increase performance significantly over the V series of suits, a far more radical approach to the aerodynamics of the suit would be required. In particular, the design of the leading and trailing edges of the wings (arm wing mostly) would be needed.
The arm is particularly poor at forming a leading edge, due to its thickness..... This leads to "separation" of the airflow from the top surface of the wing and lift is lost. I believe more realistically that no lift is produced from the arm wings of most wingsuits during flight, as most pilots think that the high force or "hanging feeling" they experience during a stall is the ideal position to fly in, as this makes the suit act like a very small parachute or "air- brake" and so they get their sacred "3 MINUTES FLIGHT DUDE!!!"
They are deriving the forward speed of the flight not through lift but through air deflection, but they get high times and so think they have the ideal position.
The lower times but more distance flights are the only ones that should be called "flights" as these are the only flights that are derived from the production of some form of lift. So increasing the performance of the suit must come from refinement of the wing design in order to increase lift and give more drive. More drive = greater glide ratio = better performance.
Getting back to cost, in order to refine the arm wing significantly, a true aerofoil leading edge must be introduced. This means that a custom made wing individual to each pilot must be measured and produced. This is because the only effective way to produce a leading edge is to have a foam formed aerofoil section supported by several mylar sections (ribs, as current V series, but mylar in every rib) with the arm inside the mylar sections or ribs. This would most likely mean that the arms could not be unzippped as in most current designs. Safety issues would be raised now.... It would be necessary to cut away the wings on every flight, as the only method of releasing the arms after deployment.
Custom measuring, custom rib designs, production time and materials costs would all increase significantly.
With respect to the trailing edge, ( the second most important part of the wing) stiffeners would be needed as trailing edge "flap" occurs on most suits now and is another cause of airflow "separation" Again, when stiffeners are incorporated into the trailing edge, deployment issues will increase as performance increases. I foresee eventually having to alter deployment methods and possibly return to spring loaded PC's activated by ripcord! This seems to be the safest way to have large, awkward relatively stiff arm wings for maximum performance and still be able to deploy a canopy.... The hand deploy throw-out is not particularly suitable for any more surface area or further stiffening of the arm wing than the V series of suits IMHO. So again expensive, time consuming alterations to rigs etc will be required to facilitate anything more than slight improvements over current high end suits.
All these issues are relevant to the leg wing as well. Stability issues will occur when the leg wing becomes much larger than current designs, and product durability problems will occur. If the leg wing protrudes much further than V series of suits, moving around on a rocky exit point / walking to aircraft repeatedly will soon cause material destruction of the suit. Nobody wants to fork out several thousand dollars on a custom suit to have it fall to pieces after a few months..... Also the more stiffening that is incorporated into the leg wing the more skilled the pilot will have to be to control a large powerful wing and not be "flown by the suit".
Wingsuits should be thought of as "lifting body suits" as most of the lift produced when flying 10/10ths as you say is derived from the pilots body IN CONJUNCTION with the three wings. A major part of the surface area of the body is covered by the rig, and the addition of ever larger "bum" deflectors on recent suits is an attempt again to prevent "separation" of the airflow and corresponding loss of lift. A logical solution is to combine the two items of rig and deflector into one, as this will give greatest lift and therefore maximum performance increase. All these new features will lead to what engineers refer to as "attachment" of the airflow to the entire surface of the top of the wing from leading to trailing edge, thereby finally allowing LIFT to be produced as in an aircraft.
But again, COST will be astronomical for all these new features. I am sure that the skydiving market is nowhere near ready for this yet (if it ever will be?) and maybe only a few BASE jumpers would be willing to shell out for a new toy costing thousands of dollars, in the hope of MAYBE doubling average glide ratio from 2.5 to nearly 5.0
2 : The idiot in the funky suit
There is no way we are going to "soar in thermals" as you put it, no matter how many dollars we throw at it, simply because we are bipedal land monkeys and not birds!!!! Evolution has left us in no fit state to fly even with a funky wingsuit. As the performance of the most recent suits to hit the market has increased, so has the physical demands on the pilot. I have found that after training with weights non specific to wingsuit flight since age 16 and now even with a WS specific workout designed with the help of friends who are PT instructors and physiotherapists, after following it for almost two years solid it is still almost impossible to fly at maximum efficiency for longer than 70 -90 seconds, depending on the day, and how close the ground is.....