I'm surprised no-one else has commented on this.
I really can't see a way of utilising the warning system to add someone to a user group for say 3 days, but to keep the points active for longer, e.g. 3 months.
That way any additional points within the 3 months would trigger the next threshold which would place them in a group for longer, e.g. 1 week.
Right now, if the points are active for 3 months then they would stay in the group for 3 months, which is obviously not going to work if that group removes posting permissions, etc. Who's going to hang around for 3 months to be able to post again?
Other than that, the only option is to use the outright ban for x days action.
Which seems a tad harsh for the first level of punishment.