Is it feasible for you to use 1300 AP with an external antenna?
you may use high gain antenna that meets your needs.
This way you are still using good coverage outdoor while not using 1500 APs. This is also useful if you want to use an omni-directoinal antenna, not a semi-directional antenna like the one integrated with 1300 AP.
This doc could be helpful for you to find supported antennas:
In addition to Amjad’s comments, an alternative setup that has been popular with several of my customers has been to use a 1262 or 3502e (and now the 3602e is available). The AP lives inside a weather-rated enclosure and you can put an external MIMO antenna outside of the box. I typically recommend keeping the enclosures out of significantly harsh or exposed places (such as at the top of a mast or in direct summer sun all day), but if you have a place that is shaded, lower to the ground, or under an eave, this setup works really well, plus you can take advantage of 802.11n whereas with the 1310 this is not available to you.
PM me if you would like enclosure or antenna suggestions.