I am going to try to elaborate, but as I have difficulties with english language (only learned at school, and gone to england only 3 weeks when I was a teen) it's tricky for me to argue in a discussion with english native speakers (although I like it because it's a good training)
so feel free to correct me if I use wrong words, wrong conjugations, wrong vocabulary, etc...
I am sure that the MK sig strat is a great guitar, well manufactured, great sounding, with a beautiful neck, body, etc...and I understand very well that you enjoy playing it, but to me that's not the point.
what I am trying to say is that making a signature guitar model makes sense only if the guitar in question has something "special", something uncommon that you don't find on a standard model.
If the guitarist plays on a "standard" guitar with nothing much special compared to a standard model, I don't see the point to produce a "signature" model.
to me, a signature model would have to make you think immediately to the artist.
I gave the example of Clapton, but as Foma said, there are many others : the tremolo arm on the SRV, the hollow frets on the malmsteen, the damaged look on the galagher, etc..
But I can't see anything on the MK model that makes me immediately think : "ah yes, of course it's the model played by Mark Knopfler"
this red strat could be played by anyone else, it wouldn't look "strange"
other examples with other guitars :
imho, making a LP signature Peter Green makes sense because it has something special (the PU wiring), but making a LP signature jimmmy Page doesn't make sense : Page played on a standrad 59 LP, like Mark's one, or EC's one, so nothing "singular"
making a SG signature Robbie krieger would'nt have any interrest imho, while making a SG signature Louis bertignac, that would be a real gem
imagine Car industry making cars signature models with car racers names....I bet you would expect some custom car, not a "standard" one
I have the same analyse for signature guitar models
maybe I theorise too much...
after all, the most important is that you all enjoy playing on this model
so keep cherish it, and play it, and I m' glad for you if you like it