Thanks for all the input regarding the limitations of the coaxial configuration when you scale it up.
The being the case, the only way to still employ the counter rotating rotors (so as to negate the need of a counter torque tail rotor) is to use the tandem configuration with the rotors interleave as in the Chinook.
I therefore thought an upsized Chinook will be a good idea for the heavylift solution. A further improvement could be to add a pair of wings and even hang a pair of forward thrust props for speed enhancements. With the wings, the main rotors may be slowed in forward flight, and part of the engine power shifted to power the forward thrust props.
Why the above was not considered?