These customers... are all them together? Or are them dispersed?
You must specify how long is the zone you want to cover, so we can calculate how many degrees do you need.
Omnitik is a omnidirectional device, and won't work fine in that scenario.
For example, if you want to cover a 2km village that is 7km away, you may need a 17º antenna, so you must use a panel.
You can even use a Sextant, buying a L4 license, or replacing the internal board with a more powerful one (how many users do you want to offer service?)
For a more professional, you can use any other panel antenna (like Itelite PRA50019) with a routerboard inside it
you cannot use omnitik, you must use a sector antenna 60°
to the antenna attach a Groove A-5Hn.
If he use SXT as CPE, as he sais, using a SISO antenna and access point isn't a good thing. It will decrease the performance and make bottleneck.
I'd recommend to use 2x2 MIMO antenna and AP