I would think that a starting delay on phantoms would be nice, atm if I want to make alternating turns for phantoms, it is impossible to do correctly. See the map attchated.
It is entirely possible to do correctly by having more than one phantom wave in the schedule - it's worth noting that when the schedule reaches the end, the phantoms will only repeat the last wave, it does not repeat from the very beginning again. For instance, if you wanted the phantoms to come every 450 frames, then you would have the first phantom gateway have a schedule with just a delay of 900 (and whatever number/intensity etc. you want), and the other gate has the first wave at a delay of 450, then another wave after that with a delay of 900.
EDIT: Since that might have been only for that specific case - if you want a starting delay on a gateway, copy your first phantom wave, then change the delay on the first one in the schedule to (original delay + starting delay).
EDIT AGAIN: Made a mistake - it turns out the phantoms will start over from the beginning at the end of the schedule. In that case, just set the last wave in the list to 9999 repeats - unless your map is excessively long this will be good enough (to put it in perspective if the phantom waves were coming every 30 seconds, then it would take 83 hours before anything would go wrong). Make the number bigger than 99 if you want to.
well, just putting a starting delay makes it so much easier.