What we do is if you are unexcused you are not allowed to meet PNMs during recruitment. Basically, you chose to miss work week or a day of recruitment for no valid reason. We will not work with you to make that time up that you lost. You are still required to be at membership selection and you can talk about women you know, but you have no vote on the new members. If women don't care enough to come to work week knowing the consequence is no say in the future pledge classes of the chapter, then I don't want them out there during recruitment anyway!
We had the same issue as you are having a few years back when I first came to advise. As soon as we started being strict about what was excused and the consequence for unexcused absences things really turned around. We haven't had any unexcused absences for a couple of years now
I do think whatever policy you decide if you are implementing it for a fall recruitment then you should let the women in your chapter know ASAP. You don't want the new policy to seem unfair and people to resent the system. If it's all out there now then you can say we informed you of the policy well before the time you decided to skip work week or parts of recruitment.