It is interesting, if not frightening, to think about what rope drop at the MK would be like now if paper FP were still in place. With Anna and Elsa and the mine train both in high demand, and many guests knowing that the only way to get a FP for either of them would be to participate in the rope drop dash, it could be pure chaos. Just picture what it is like now and throw into the mix a high percentage of the guests who stay away from the horde because they already have their FPs in hand.
We all know what it was like at TSMM when lines at the FP machines extended back to One Man's Dream, FP return times quickly moved into the afternoon and ran out completely within 2 hours after park opening on busy days, and the standby line grew quickly to an hour or longer and stayed there all day. There was also the fun of being in the standby line while the FP runner pushed his/her way through to join the rest of the family so that they could get two rides on the park's most popular attraction, leaving many others out in the cold.
I don't know for sure what the capacity is for the mine train, but with the generally larger crowds at MK compared to DHS, I suspect that FPs wouldn't even last an hour on a busy day, and if the return time when you happened to reach the machine didn't fit your schedule, or conflicted with an ADR, you would be out of luck unless you were willing to wait in a massive standby line. It would likely be impossible to get a FP for both on a busy day because the FPs for one would be gone within two hours after you get a FP for the other.
Be careful what you wish for. The mine train with the old paper FP system might be more frustrating and more physically intimidating than the current situation. While a lot of people use the mine train as an example of the problems with FP+, I think it's an example of why something like FP+ is needed for high demand attractions to give as many guests as possible a chance to enjoy the attraction and to make guests as safe as possible.
Just my opinion.