No rigging really, it's commonplace to pick up power from a keypad or a pigtailed power connection. Other manufacturers make keypads that have 4 zone inputs on them, so it's not an unconventional practice, and with a lot of other systems or installations, it's even more common to see junctions behind the keypads, as they're still accessable after the fact without having to go digging for them.
Irregardless, you should always have extra ampacity on the panel for devices anyways, it's a best practice.
Irregardless, you should always have extra ampacity on the panel for devices anyways, it's a best practice.