The water meter You have is an Ista 16093, part of domaqua m series.
The grey area of the meter is where can where can be added a pulse generator.
The pulse generator add on can be found in Ista catalog.
https://www.ista.com/fileadmin/twt_customer/countries/content/Unitedkingdom/Documents/ista_water_meters_brochure.pdf
That said, evaluate the price and compare to others water meters with pulse output, since many times the prices for that modules are very high when purchased in few units or not being a company working in the sector (discounts are very high), sometimes higher than buying water meter + pulse generator.
In my opinion is better to have LoRa pulse counter as separate unit.
As for tampering, the LoRa (or not LoRa) pulse count units, can have anti-tampering function (cutting the wire a pin in the LoRA module change state and an alarm message is sent and/or status bit is changed).
Otherwise that function can be disable and used only 2 wires.
Lately we were testing some Adeunis LoRa units (ADR8230AA).
It is two channels pulse counter, so can be attached to two meters (or one 5 wire meter).
p.s.: I don’t work for Adeunis or any other meter manufacturer company.