It has some similarities and differences, at WDW, you get three FPs to start with and once you use the last one you can get another from the app from anywhere within the park, so that is similar.
Really everyone using MaxPass wouldn't overwhelm the system, as everyone can still use regular FP which are all part of the system, but MaxPass does get the added advantage of being able to pickup FPs that other guests have cancelled.
It is definitely not going to fail, it works amazingly well and FPs aren't disappearing at a faster rate because they seem to have found ways to make the queues more efficient with the new system. Really most FP return times (Except Guardians, RSR, Star Tours and Space Mountain) are almost always available with immediate return times or at least return times that are sooner (usually less than half) than the length of the Standby lines, including Splash Mountain and Grizzly on very hot days, yesterday the latest return time I saw for either of them all day was about 30 minutes later.
I do think that we will and should see FP added to more attractions that need it and can handle it, for example I could see adding it to Peter Pan if they rework the ride a bit, with just a little reworking of the queues they could add it to Storybook Land Canal Boats and Casey Jr Circus Train and Alice in Wonderland could benefit from FP as well, what you don't want is it added back into Pirates, it made the capacity drop dramatically, although with how they are doing FP now it might not be the same issue now, it could also work at Jungle Cruise. I could also see them bringing it back to it's a small world holiday, maybe even making this one only available with MaxPass so they don't have to setup machines to distribute them as that was the biggest issue they had there with FPs. I could see it returning to Autopia as well. They could even start adding certain character locations to FP, such as Mickey's house, Princess Fantasy Fair, both of which are setup in such a way that they could handle FPs.
Really the new setup is massively improving capacity and reducing how crowded everything feels and is even reducing the length of standby lines, so really it is good for everyone and I would expect it to be expanded where possible.
A side effect of MaxPass is that it is also reducing issues for those with a
DAS, as the waits when you return are shorter and if they have MaxPass as well they can utilize a combination of the two to reduce the number of times they have to go to kiosks to get return times, thus minimizing a lot of the extra distance they were having to do. So really overall the system has already been a massive success.
And this is coming from an annual Passholders that absolutely wanted to hate it, in the end I have found out how much more enjoyable it makes the parks and I am very glad that we decided to spend the extra $6 per month on each of our passes to get it, for us it was money that was very well spent. And yes, I do wish they would simply include it, but there is another thing that no one really mentions that adds to the value of MaxPass, those with MaxPass can access FPs that others have cancelled, which means that someone may be pulling a paper FP for an hour from now, but with MaxPass, you might score one that is available immediately. This does add some extra value to getting MaxPass.