It'd be interesting. Getting all 300's to the end of the song, you have only 4-5 notes left, You are placed 10th on the map, then completely f up the final stream. You'll end up dropping from 10th to 500th. If we take this route with the scoring system, this is exactly what's going to happen. Scores won't be just scaling up, they will be increasing / decreasing as you play through the song.
An issue that I think would have problems is the lower diffs where there is literally only 1pp or a few extra points in Aim/Acc/Spd difference between each mod. That means anyone who can spin would only have to run two mods (DT HR) and they'd have a first even on medium length spinners.
At this point, having an option to sort by PP earned would be better than having the scoreboard adjust since it wouldn't be the top PP players in first. The current system also has this problem, but I see it being even worse with the new system since mods no longer would give a set value, and would probably make the multipliers within only a few decimal places of each other because of how close they are in performance.
It depends on how it is calculated as I'm no mathematician to be able to even comprehend how it might be calculated, but the difference between mods on easy songs, and mods on hard songs is extremely big. We have to make sure all ranges of difficulties can be calculated properly.
Just some things I thought of while reading through this thread for a few days. I'm not against this, nor am I supporting it. I'm just going to stay neutral in this whole thing.
PP is out of my reach with this new system since it doesn't work to my style of playing so I've honestly just given up on it. I've never really been competitive anyways, no do I care really about improving my speed skills. I'd rather improve at something I have fun doing (Flashlight and 100%ing slow songs no one has before.)
Is this a good idea? Yes, very much so. However, I still think there are lots of problems that need to be taken care before we can safely transfer over to it. Many of which have already been listed. Right now I think it is way too early still to be pushing this feature as hard as this thread seems to be wanting to. The system isn't even closed to being finished with the other modes, Seems like there is still some balancing issues to deal with, etc. If there is going to be such a big change as switching over to a different method of scoring, everything has to be completed and ready to go, doing bits and pieces at a time would make it a disaster, especially with how delicate the system is with reasons you (kyou) and tom have mentioned.