The 'reduced' cash will be due to the fact that the freighter flying can be 'unproductive' with lots of down time. The pencil pushers want a cost 'per hour' balanced into a 'month'. In other words, they want to pay you less, since you fly less, yet still be away more.
The problem with a commuting roster for EK is that they are competing with BETTER contracts at other companies. Why would anyone come (or stay) to fly 28/13 when they can go to Korean (19/11) or China or.............
You add in the fact that for most countries (where you will reside) there are tax treaties. Not so with the UAE so you will pay tax on the full salary.
I'll reserve more comment until they actually publish the conditions, however, just guessing that it will be bare minimum. I'd also suggest it may be a way for them to test the waters to see exactly how LITTLE they can offer. If enough EK/outsiders accept it then they know they can keep conditions soft.