I think the LFG system should be a complete opposite of this.
Have groups listed with members, roles needed, instance & time to start plus a comment.
Make it so you can plan your night of gaming in advance.
I don't really want to "plan" my groups, though. When I want to run a Flashpoint or Heroic or Operations, it's because I benefit from or need that mission completed to move and don't want to wait around for hours or plan on doing "later". I feel that with a time to start it would just generally say "Immediately" because most groups are planning on running as soon as they find a full group. Especially when only four people are needed, the roles needed would be useful but overall would make the process a little redundant.
For operations this might be a useful idea, otherwise a system that doesn't involve extended amounts of time of waiting or looking would be nice. Planned things are generally only useful for group of friends or colleagues.