Leaving aside the ethics and morality of "changing" the contract after it has been agreed, how much will this cost the employee?
Suppose you need to spend ten nights a month in Dubai during a 28 day pattern, including one at the beginning and end. Days off etc down the line are covered by the company. If a hotel can be had for USD$100 a night then the cost is USD$1000 per 28/13 pattern. Given that there are nine 28/13 patterns in a year then that would make the cost around USD$9000pa.
So not an insignificant number. However it would depend on what quality/price hotel one is happy to accept in Dubai.
The freighter contract is around US$118,000 pa (AED432,000 pa) including the accommodation allowance. So it becomes around US$109,000 pa.
Do these figures seem reasonable? Reasonable as in ten a month at US$100 per night not reasonable as in fair.