This is very similar to my own ESP-Now projects. I was very impressed with the range one can achieve with simple external antennas.
I’ve been using the “ESP-Now-Burst-Serial-Bridge” linked below as the RTCM3 relay for my Rover mower for the past 2 months with no issues at all. I see ranges over 200’ on a regular basis with no packet loss, even through some significant physical obstacles.
ArduPilot blog entry
ESP-Now-Serial-Bridge (github.com)
ESP-Now-Burst-Serial-Bridge (github.com)