He may be an attacking footballer, and if that's the case, he's not a very good one. Doesn't get nearly enough of the ball for mine.
He does have a penetrating kick WHEN he uses it, but more often than not he tucks the ball under arm and off he bolts and then puts himself in a panic and get's caught. He hasn't got the smarts to make decisions on the run - which is an unfortunate fault in someone who's strength is his run.
Unfortunately you have made some good points there IMO. He is a baffling player because he has such obvious strengths and weaknesses and it seems impossible to position him in a way to isolate one over the other.
I think we have rose-coloured glasses to a degree when looking at MM on the wing. Stats may prove me wrong but he wasn't a great possession winner (maybe not smart enough to get in right positions or win the ball in traffic, which is a big issue if rotations bring the wingmen into the centre for periods of the match). Also his goalkicking accuracy wasn't great (again stats may prove me wrong). On the flipside he often gained us good ground when he got the ball and applied tremendous defensive pace/pressure through the middle which we have sorely lacked this year.
So where to play him?
Not good enough on full-back line, we have better options off half-back given his clangers/decision-making in traffic back there, would be a pacy half-forward but innaccurate and lacks the smarts to get the ball up there (though that hasn't been tested).
Personally, i still reckon the wing is his go despite his limitations, and he is in our top 2 wingman still IMO, so despite the above I am still on the Marty for Wing bandwagon