Bangoman
Sorry, Steve, I've been offline for a few days. No, not offline; just disinterested enough in everything to not feel like participating. 🙂
I don't think SL will fly as an OTS for two reasons:
1) How would you ever have enough stock to accommodate all the different lengths that would best accommodate each person. To have an OTS SL iron, you would have to require everyone to play the same SL. That doesn't make sense to me. Sure, you could force everyone to play the same 7-iron length and that may even be better than having variable lengths, but I don't think that it is the optimal (or maybe even an effective) implementation of the SL concept.
2) An even greater problem is that the best SL iron will be one that really suits the player in terms of feel: length, weight, balance. Sure, we might be able to adapt to the "unfitted club," but to really take advantage of the SL concept I think you should find the club that actually FITS and duplicate it across the set. Then you really have something. Otherwise, you just have eight clubs that may or may not fit you. Great -- now you could have eight irons you can't hit!
I played 1Irons for several years. They were decent; maybe even good. And at least they were semi-fit for length in that at least David took a WTF measurement. That's not perfect, maybe even not good, but at least it's something. I quite liked hitting the 1Irons. I once even put them in my trunk as I tried returning to my Snake Eyes 600Cs (which I loved and still love). I changed back to the 1Irons at the turn.
Hitting a SL iron truly is comfortable and so much easier than hitting variable length shafts. However, I eventually did ditch the 1Irons because I didn't like the feel of the shafts and the balance of the clubs. They were "boardy." Now I had eight boardy irons in my bag. If I could have built them to my feel with the shaft I wanted, they probably would still be in my bag. I think you can address these different IMPORTANT variables with component, SL irons: length, weight, shaft profile, and balance. That's too many variables to be addressed by the OTS. Just my opinion.
(Hope this makes sense -- I've had alot of scotch. 🙂 )