Could lead to elitism and stop fresh new players. I do agree with the principal of it though as it does become frustrating, i dont mind when people post im going on hol for a week, sorry for inconvenience.
2 suggestions : An annonymous comments section in the players profile, comment -> mod -> attaches ?
A sticky at the top on guidelines for new players looking to start pbems would be good (beware they're long, dont get in too many, would you suit ip player better etc).
First come, first served - nice all invited welcoming game however it does have the most stalls and drop-outs.
Judgement of CMN - It's unlikely hes going to know many of the people so his only option is going to be length of time registered with poly really and its not that often its an experienced player setting up a pbem, most of the time it is noobs looking for their first MP experience.
Seniority - Well it would be nice to kick the arse of somebody ranked above me

then again i can imagine the enthusiasm dropping out of a player when hes shoved aside for somebody else, i believe a courtesy among players would leave this as nothing more then the first come first served.
Points system - slow player, points lost. Drop out - big loss. Gains for completed and being quick and good sport. This seems a good idea.
Then again how many people can say they've completed more then half a dozen games so the points difference between the vast majority would not be much.