The one flag thing is up to the mapper, really. The auto-kill is an interesting idea, and could potentially counter other issues in the game (ie: excessive defense once a team has the lead), but it adds more complexity and tries to force people to play a certain way. I could see it causing a lot of problems.
Enabling respawn probably wouldn't be the best idea, especially since you get points for holding the flag when a team is eliminated, so some people could come into the base of the eliminated team, sit on the flag and spawn camp them, racking up tons of points. Perhaps what we could do instead is disable respawning for every team once one team has been eliminated.
For the scoring, there are a couple alternatives to winner takes all:
- Every live team gets a point when a team is eliminated.
- The team that eliminated the last player gets a point. Either all or none of the other teams would get points on a suicide. It would probably have to be the former as the latter could be abused -- people suiciding to prevent grabs and getting no point penalties.
- Each kill counts as a point, as b00nlander suggested.
In the first idea, a team could still get points by sitting back and not doing anything, but the other teams would get points as well. The second would ensure that only teams partaking in the battle get points, but it might just be the team snatching the last kill when another team did most of the work. The last idea would probably lead to rather quick matches, as it wouldn't take a team long to total 50 kills. In siege mode, the offensive team used to have such a distinct advantage that the whole defensive team would just suicide so they could attack. With the new mode, though, it's about even with 5v5. Defense can get 6 points and offense can get 6 points.