Im far from convinced he can be a genuine lock forward.
If I was devising a game plan to keep Latu and Doueihi (and Bula) on the field, Doueihi would have the 13 on his back and defend in the middle but would play right side in attack. Latu would defend right half position but be the first receiver in attack, some might call it a ball playing lock role but it is more of a true halfback role. I think Latu is a natural first receiver and Doueihi is not, more a second received.
Now I mention Bula because I think for this to work he needs to be a constant presence up the middle 3rd be it taking hit ups when required, as an inside runner for the 2nd receivers or a support runner for the forwards or if Latu wants to take on the line.
Now I appreciate this would put a big workload on Doueihi. One I'm not sure he is capable of doing for 80minutes to be honest. I think you vary between starting him on the bench and playing a genuine middle forward for the first 15-20 or starting him and attacking edges early before trying to run through their middle late in the half. This is where Api should be thriving with Latu and Bula alongside him.
Nothing personal either but what someone else is earning should have no bearing on what he is offered. It certainly may influence his self evaluation but wasting money on others doesn't justify what we should be able to spend on Doueihi. I'd put this alongside the "loves the club" type arguments.