Would love to use custom fields in trigger criteria.
Realizing this is a bigger issue than it seems, even something possibly simpler like:
5 OR provided unassigned boolean fields. We users can use them for whatever purpose we need. Then we can include them in the criteria.
And along that line, would be good to have a field we can put in the checkout form that has language permitting us to SMS to guests and acknowledging that may incur carrier fees. We can then use that field in Triggers to determine if a specific user will get an SMS or not. Then have an alternative trigger to handle the "No" people.