It's a good question and the one that has no simple answer... or any answer.
Don't forget that "Mark's guitar playing" is not something he invented single handedly, it has elements of J.J. Cale, Chet Atkins, B.B. King etc... From my understanding, the term "it sounds like Dire Straits" originated long after Dire Straits debut album and everybody was like: it sounds like J.J. Cale, Chet Atkins, B.B. King etc... He got extremely lucky since he was born in the right time and in the right place, which obviously nobody can imitate. When I was a kid I wanted to play on every guitar with my fingers long before I knew who Mark Knopfler is, I just dig the sound like he digs it, so it's not so much of a unique idea to say the least.
Nobody can imitate someone's guitar playing or songwriting, but if you're talking about "sounding like MK", it's hard because it rely more on skill rather than on gear (same thing with many many many of great players, by the way). But you can start to "sound like MK" by taking a Stratocaster guitar, any Strat out of the box and engaging bridge and middle pickups on any amp. It's like if you want to sound like Django you buy a Selmer-Maccaferri style guitar and boom — you sound exactly like Django!
I don't think that it's really hard to imitate Mark's guitar playing as much as it has no purpose, because he already sounds like MK enough. It makes sense if only you're going to become so great that like with Mark himself, everybody will forget you imitating and remember you becoming yourself, but it's hard to do, because MK is a genius and that's really what is hard to imitate.
I believe it's quite hard to imitate Mark's playing. he developed his style by studying and playing old ragtime blues. this requires strength and coordination, good right hand rhythm, good pulse, etc..
I never saw a cover band doing it right.
I am wondering if the 'genius' can be trained, if you follow the 10000 hour rule, and practice hard.
I’m not really talking about copying 100% because you can’t ... because of all the details like pickups , guitars, amps, it’s almost like crazy complicated but you can get close to the spirit of Mark's playing by studying hard all the nuances.
Remember that Mark had and still have many relatives and friends and also 4 children and nobody has yet exceeded or even gotten close to his level of genius, it means that even if his closest actual relatives and friends can't touch it, obviously we mortals can't get to this level even with 100000 hours of practice.
With that said, if you look closely you can see Mark plays pretty much same little things throughout his whole career, I believe you can hear him playing the same "Mississippi Blues" all the way from his late 20s to 70, so for almost 50 years straight (at least on camera). And he quite obviously lacks some deep guitar knowledge and can't be up there with all the technical greats and virtuosos like his own bandmate Richard Bennett.
I have to say that Mark IS a virtuoso on his own right before somebody would throw a rotten tomato at me though. I guess with Mark this old saying goes well: "I fear not the man who has practiced 10000 kicks once, but I fear the man who has practiced one kick 10000 times". Meaning that Mark put all his efforts into developing his own style and has become a virtuoso at it, while sacrificing really deep blues/jazz/country skills, which seems not to bother him at all.
