My suggestion would be to have a semi-traditional backpacking store with the familiar well known name brands and slant your inventory towards the light weight options.
Then stock other "non-traditioanl" name brands that we all know and love.
Better to have a mass appeal of gear for your meat and potatoes to pay your bills and to get clients into the front door of your store.
Then in the process of talking to the client, you can offer them the option of lighter weight gear.
Be the store that offers the expertise and service about traditional and lighteweight backpacking gear....as they say, "Become a resource for the community" and they will come to you for that vs. your trying to have the lowest price.
I think that having a brick and mortar store just for light weight camping would be too narrow a niche with a limited amount of people able to travel to your location.
So, I would then agree with the comment above about having a website to sell the lightweight stuff, if that is all that you want to carry.
Have a store that also offers inhouse classes and lectures on backpacking...ie. "How to lighten your load on the trail without shivering to death.". Offer outings/trips/dayhikes for customers to join you on when you can offer to educate them while having fun.
You might find that you are creating a community of local, loyal clients who will spread the word about you to their friends, co-workers, and family.
The side benefit is that on these trips, clients can see new gear in action, try it out and then maybe buy lighter stuff to replace the more traditional stuff that they have previously bought.
My thought is that for many people, transitioning to light weight is about being mentally comfortable with it...baby steps. Often requiring buying stuff and then gaining experience and then buying lighter stuff to replace the prior stuff.
Physical location is definetly important, but the next thing to do is find out how you are going to differentiate yourself from the local competitors and the internet....to me, the answer has to be what you personal bring to the table....experience, expertise, force of personality/passion, and service- things that don't cost you much in dollars, but make all the difference to a perspective client.
In terms of demographics...my observations on the trail are that backpackers are often young/poor students (20's) who have the time and phsyical ability to backpack but are on a tight budget and the other group are those who are retired (often men), who have the time and often do have money to buy all the gear they want or need.
One area that I see a huge opportunity for lightweight backpacking are young families...middle aged parents.
They may want to take their children backpacking, but find it impossible with traditional gear because of the sheer weight that would need to be carried.
Speaking from experience, using the lightest tradtional stuff that I could buy for my family and I, I was left with a 80 to 90 lbs of gear on my back for a family of three. (Parents have to carry all the gear for the kids)
To me, going light weight really is the only option.
Think about it, how many car camping families might want to go backpacking with their kids, but can not because of the sheer weight of what they would have to carry of traditional gear?
So perhaps the missing market are these younger families who car camp vs. backpacking?
And yes....the other people that you mentioned, hunters, photographers, etc are a good market, but bear this in mind....for them the backpacking stuff is a distant secondary issue to their primary passion (hunting, photography, etc), so they may want to go light, but may not be willing to spend top dollar on the gear. My evidence of this was visiting a Bass Pro Store that opened up not to far from me recently. The camping stuff they had was heavy, cheap, and just barely lighter than car camping stuff. But it made sense to me because they were just stuff on the side that the outdoor person "needed" in order to enjoy their sport/hobby/passion.
Anyway, hope that this helps....curious to see what you end up doing.