I think you might attract those who like a 'club' atmosphere and being around like minded individuals for a day, you get those at powered clubs as well, people who will pop down for most of the day.
However, for a lot of powered pilots who have been used to booking an a/c out for an hour, maybe arriving an hour before and leaving an hour afterwards, after having had lunch with wife/significant other in the club restaurant, asking them to spend 12 hours and the rest at a gliding site in the summer with chocolate bars and soft drinks in a cool box and a nice dry patch of grass for significant other to sit on with maybe a couple of ten minute circuits (or indeed no flying at all) may be as you say a bit of a shock.
I have a foot in both camps and it's a completely different culture. I may of course be totally wrong but that's how I see it. I wish you every success, personally I would like to see all powered pilots get to at least solo standard in gliders before they move to powered purely for the skills it teaches, much as I would say every car driver should ride a motorcycle first, but if you can afford to rent/share a powered a/c, go places in it with one or two other people, what's the attraction in gliding? Unless you're a flying nut (like me).