Possible, yes -- just about anything is possible -- but introducing another choice is a bad idea, plus it would increase the support necessary. (Like, now all of a sudden you'd have to test changes in even more settings and configurations. It's already bad enough. There's a reason one of the first things we did was kill S1.)
(Also, it wouldn't be "S3", since S1 vs S2 are actually journal customization systems. The fact that the new design only applies to S1 right now is a very long explanation and only partially relevant, but essentially: they probably started with S1 because the S1 concept of "journal entry page" was ridiculously old and needed an update desperately: S2 handles journal entry pages through the journal customization system, not through the site templating system that S1 uses. Way back when Brad started work on S2, he intended for all entry display pages to be handled through the journal customization system someday, because the old code was really really old and inefficient, even back then. On DW, every entry page is displayed through S2, believe it or not, even if it's site-styled comment pages: that way we only have one code pathway to maintain.)
But, yeah, offering an opt-out for a full redesign is very, very rarely a smart choice. If you scroll down to "Will new features be opt-in or opt-out?" in our pre-open-beta business FAQs I go into it in more detail, but essentially, it's easy to do an opt out for a new feature (if the opt out isn't just "okay, so don't use it then!") but it's often counterproductive to do an opt out for a new design. We're back to the decision fatigue again.
no subject
(Also, it wouldn't be "S3", since S1 vs S2 are actually journal customization systems. The fact that the new design only applies to S1 right now is a very long explanation and only partially relevant, but essentially: they probably started with S1 because the S1 concept of "journal entry page" was ridiculously old and needed an update desperately: S2 handles journal entry pages through the journal customization system, not through the site templating system that S1 uses. Way back when Brad started work on S2, he intended for all entry display pages to be handled through the journal customization system someday, because the old code was really really old and inefficient, even back then. On DW, every entry page is displayed through S2, believe it or not, even if it's site-styled comment pages: that way we only have one code pathway to maintain.)
But, yeah, offering an opt-out for a full redesign is very, very rarely a smart choice. If you scroll down to "Will new features be opt-in or opt-out?" in our pre-open-beta business FAQs I go into it in more detail, but essentially, it's easy to do an opt out for a new feature (if the opt out isn't just "okay, so don't use it then!") but it's often counterproductive to do an opt out for a new design. We're back to the decision fatigue again.