I 'm not exp. but in my games I had the sense that "original" possession of the match were coming from the quality of the middlefields. So I 'm thinking that if in this formation AM and DM doesn't count as real M, there will be a permanent problem in possession.
Also I'm not sure if it counts as illegal and what possession it 'll give because things are little messy lately.
Also these positions (DML-R and AML-R) are dif. to find many good players and reserves.
The good thing is that your opponents will not (because they will not find) set any counter formation so you 'll be sure that they 'll just play with their favourit formation.