3rd Party Antenna

Antennas are not in my realm of expertise. I have a location with a tower. I would prefer to leave the gateway at the bottom of the tower and run a coax up the tower to the 2 LoRa antennas.

Are there any consequences for doing this? Can I use a larger antenna? If so what parameters of a 3rd party antenna should I follow?

Also is there any “positioning” recommendations?

Hi. The best way is to put the Gateway on top of this. Using a long cable will degrade the signal quality.
I suppouse that you talk for RAK7249 Gateway so RAK options for antennas are here https://store.rakwireless.com/collections/antennas/products/fiber-glass-antenna?variant=27103006359652 and cable here https://store.rakwireless.com/collections/antennas/products/antenna-feeder-line
Keep in mind that if you plan to deploy this in the field you will need lightning arestors also https://store.rakwireless.com/collections/antennas