You need more angular separation between the units to do frequency reuse. I have done frequency reuse with 30* horns at 60~70* azimuth separation with OK results, but in your case you will have some overlap between the two AP’s and stations will hear both AP’s simultaneously.
I don’t think that will work as you hope. The way that Frequency reuse works is both by the GPS synchronization keeping the TX and RX portions of the frames synched, but it also needs separation so that each SM only hears it’s own AP, and that each AP only hears it’s own SMs.
Without enough separation (either frequency or physical separation) then when AP#1’s SM#4 is ‘listening’ for it’s data from it’s AP, that’ll be exactly the same time when AP#2 is TXing to one of it’s SMs… and the two will stomp on each other.
I mean, some of it might work OK – folks far enough out to the sides - but if you’re overlapping both frequency AND the coverage beams, then IMHO, it’ll be a mess.
If it is 40° from center to center of each 60° horn/AP then it looks like there will be 10° of overlap in the middle… you might get away with it as long as there are no customer radios in that 10° of overlap but I think even then it would be problematic.
To be clear, the AP’s in this scenario are not the issue as the GPS sync should keep the access points from ever seeing each other regardless of what direction you have them pointed. However, single client radio that can see and be seen by another AP using the same, overlapping or too near the same channel/frequency will wreck everything regardless of Sync.