Pretty soon I'll be committing my "balancer set" patch to httpd-trunk. This basically allows for member sets within a balancer similar to the 'distance' mod_jk attribute. What it does is allow for more control over which members will be used via m_p_b. The logic is:
Look for all usable members in set #0 If none exist, look for any host standbys in #0 If none exist, select the next set and loop I think this design provides the most flexibility for the admin. Anyway, this will require an update to the pertinent data struct to add the "set" element. I will also at this time likely add a "busy" element as well, in anticipation of the by-busyness LB method patch ;)