I just posted a number of questions under the Eastern US forms about this route. This route used to be in the AMC guides and i'm fascinated about whatever happened to it. I'd be interested in what you know about it since you clearly have done it. This is the only report I can find on this old route.
This photo indeed makes it look very intense and fun!
Copy and Pasted here too.
As far as my experience with Chimney Gully goes it is strictly a winter climbing route for me. In the winter the climb is a straight forward snow and ice gully and only in lean snow years or random times is there ice 3/4 the way up the gully. The ice section is easily climbed by anyone competent on WI2 although the run out is 900+ feet of rock and hard wind pack snow. The issue with climbing this route is not the technical difficulties it is the fact that it is an avalanche terrain trap. The climber is locked in a gully for 1200 feet, and depending on the speed of the team upwards of 4 hours in a funnel for avalanche debris from above.
I have no experience with this route in warmer months, and would be willing to bet it is a horrendous bushwhack of an approach, rough climbing through krumholtz trees in spots and only fun after you are done and can say you muscled up path not traveled in decades.
BSP may have issue with you thrashing around "off trail" in summer, during winter off trail travel is not as heavily frowned upon.