Have leader's permission emails indicate whether assistant leader or participant
As a trip leader it'd would be nice if the permission request emails specify in the subject whether the request is for a participant or an assistant leader. This way the leader could handle emails differently, i.e. use different email rules, or simply, trying to make sure they have enough leaders earlier than accepting participants. Maybe a drop-down for the type of request or separate links would be a solution - i.e., "click here to request permission as participant" and "click here to request permission as leader"
It was easy enough to add a question to the request, there does not seem to be any downside, and there are a few activity types where assistant leaders register themselves, so this is done.