Personally, I'm not sure it's possible for SE to offer sufficient rewards for this, barring something truly ludicrous. In the time it takes to run a single Roulette for MSQ, someone can easily run 2-3 Level 70 dungeons. Are they going to start offering a couple of hundred Creation Tomestones alongside 50+ Mendacity? That would probably do the trick, but oof.
I also would argue for a return to the old system (over this current edition). I disagree with your reasoning, or would argue my position, based on two points.
(1) This change impacts a tiny minority of the player base. The vast majority of players have already cleared the storyline at least once. Only brand-new subscribers, or the relative few who subscribed but abandoned XIV prior to the MSQ missions, will ever benefit from this. Was it really worth rocking the boat this badly? SE had to spend time to develop this change; they're now having to pay attention to nontrivial queue impacts - and even that might not even work. This is one of those points in time when a half-assed solution simply doesn't make sense. Had this been timed for the launch of a new expansion, sure, I could maybe see an argument (particularly if the measure was temporary). Right now, though? Either fix it the real way (make it a solo instance and/or relocate the cutscenes), or don't touch it.
(2) The previous system did not make it impossible for new players to enjoy the MSQ the way it was originally intended. It simply made it impossible to do so using the Duty Finder. Yet, every day, there are plenty of Linkshells advertising themselves to players of all skill levels. There's also the Party Finder. Players have always had options. All SE really had to do was warn people; something like "due to the nature of these missions, Duty Finder is not likely to provide the recommended experience." Granted, that would involve admitting fairly publicly that they f***ed the pooch for these missions, but it's not like it isn't obvious to 99% of the existing player base. Either way, though, people have always had options. To act as if they were compelled to join the content through the DF is wrong.