It might be best to do a combination of other senior members, antipoints, number of posts, positive contribution to ao's other members and whatever else jp suggests.
Personally this junior/regular/valued/senior stuff might or might not have a bearing on advice given from members. What about a split rating based on some of all the suggestions posted here.
JP - what about a "hot button" to help you calculate the VALUE of antipoints such as, at the bottom or top of each post a member could click on "did this post help?" or something to that effect.
