The knee jerk reaction might be to think that, but when you think it out I think there is a better argument to be made for the opposite, that only alternate breaks ensures both players can stay in stroke and that winner breaks often keeps players in their chairs getting iced and out of stroke. With alternate break you will be at the table at least every other game which makes it difficult for any player to get out of stroke.
It does not prevent break and run packs. You can still run a pack of any length up to the amount of games need to win the match, they are just interspersed with the games where your opponent gets to break. In fact, in say a race to 9, you can run a 9 pack, and your opponent can run an 8 pack. Packs are not in any way stopped under alternate breaks. People make a much bigger deal about the fact that the pack is interspersed with the games where the opponent is breaking that what it really is. In winner breaks you have to wait between the games while they rack the balls. Sometimes you have to wait while they take a restroom or smoke break. There is always waits of varying lengths as it is, so alternate breaks is just a different reason to wait in between the games in a pack than the ones we already have, it really isn't that big of a deal, it just isn't what we are used to but we would get used to it pretty quick.
Once the version of the modified spot shot they are using is determined to not be difficult enough they would obviously just back the object ball up even closer to the back rail and make it tougher. Or just add more levels of difficulty than they currently have (which is two) by starting to back the object ball up closer to the rail for additional difficulty levels beyond the two they already have.
I also wonder whether or not I would prefer a rotation of types of shots instead of just a single modified spot shot. Like the first shot is a modified spot shot, the second is a bank shot, the third is a jump shot, maybe one or two more types or variations of shots, and you rotate through them as many times as needed. Not sure how feasible it is or how much more I would actually like it but it does attempt to address the repetitiveness and add more excitement.
I don't see the need since alternate breaks solves all the same issues even better, plus solves other issues and comes with additional benefits that your version doesn't. If they did a tournament your way though I would certainly check it out and give it a chance to confirm but I think I would much prefer winner or alternate breaks rather than something that tries to be some of both and as a result doesn't end up doing anything well and actually just ends up with the problems of both of them.