Our Personalized Touring Plan software supports the "big" character greetings that have posted wait times, are continuous scheduled, and have well-managed queues (for example, Meet Mickey at Town Square Theater at Magic Kingdom).
Unfortunately, we do not have the necessary data about schedules and wait times to make reliable predictions about other character greetings.
We understand that lots of guests like to meet characters, but doing so is seldom a time efficient activity. One acceptable workaround may be to add a break to represent the chunk of time that you'd like to spend meeting characters. Be sure to allow plenty of time: some characters can be quite chatty, and the lines can move very slowly due to that and character break schedules.