It would work better as a "transaction" night. members could post if cards are FS/FT or FT or FS or whatever. I would definitely be their as a buyer and in a support capacity.
If I had to guess, I would think that the majority of people would be afraid that "transaction night" is just a few people trying to see if anyone wants to buy a Wil Myers BGS 9.5 blue ref auto for $325 ($20 less than ebay!). I would be happier selling a quarter of that in inserts and parallels that I'd like to move.
Just as good would be trading them for similar cards that I want. It does not seem that many see it as worthwhile to dig out a couple of 2012 Bowman Internationals or some $3 Craig Counsell inserts and sell them here. I would be very interested if someone was selling those here, but so far I haven't seen it. Hence, the hope that it leans more towards trading than buying/selling.
Or maybe just a night where everyone posts their wantlists. Similar to a show where you just walk around and tell dealers what you're looking for and he/she pull out their Craig Kimbrel cards or points you to the box where they are. It's a variation of the player collector thread and set builder forum, I suppose, but would allow for both player collectors and set collectors to try to find what they're looking for in one place.